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Biomedical subjects

C A Fox

Publications and source records attributed to C A Fox.

At least 55 records · Page 3Linked to original sources
PubMed1987

Injury and physiological responses of Larrea tridentata (DC) Coville exposed in situ to sulphur dioxide.

The response of shrubs of Larrea tridentata (DEC) Coville (creosotebush) exposed to sulphur dioxide (SO(2)) was evaluated using in situ plants of the Majove Desert. Larrea was exposed to acute levels of 0.3 to 2.0 microl litre(-1) SO(2) for periods up to 13 days using field chambers or an open-air fumigation system. Plants exposed in the spring exhibited considerable leaf injury (necrosis and defoliation) when exposed to 2.0 microl litre(-1) SO(2), and in the autumn had leaf injury when exposed to >0.4microl litre(-1) SO(2). Injured plants had higher transpiration rates, less negative water pressure potentials, and/or lower photosynthetic rates than control plants. It is likely that Larrea would not be injured by the typically low SO(2) concentrations and dry environmental conditions of the Mojave Desert. However, if injury were to occur, it would be accompanied by changes in plant-water relations and photosynthesis, followed by recovery after the SO(2) stress was removed.

Journal Article↗
PubMed1987

Sulfur dioxide effects on plants exhibiting Crassulacean Acid Metabolism.

The effects of SO(2) on species exhibiting Crassulacean Acid Metabolism (CAM) were determined with short term-high concentration 'acute' greenhouse exposures (0.6 to 3.0 microl liter(-1) (ppm) SO(2) for 2 and 8 h), and long term-low concentration 'chronic' field exposures (0.35 to 0.90 microl liter(-1) SO(2) for 32 to 79 h periodically over 7 to 13 days). In the acute greenhouse exposures, visible injury was observed on Opuntia basilaris Engelm. & Bigel., exposed to 2.0 microl liter(-1) SO(2), but no injury was observed on Ananas comosus (L.) Merr., Bryophyllum blossfeldiana Poelln., Bryophyllum pinnata (Lam.) Pers., or Bryophyllum tubiflora (Harv.) Hamet, exposed to up to 2.8 microl liter(-1) SO(2) for 8 h. Stomatal conductance during the exposures averaged 0.067+/-0.021mol(-2)s(-1) for Opuntia basilaris, 0.029+/-0.008mol(-2)s(-1) for Ananas comosus, and 0.029+/-0.008mol m(-2)s(-1) for Bryophyllum pinnata. Opuntia basilaris was injured early during the day, but not at night; with the injury appearing as a white necrotic banding across just fully expanded pads. Moderately injured pads would regreen beginning 1 to 2 weeks after exposure. In chronic field exposures, no visible injury from SO(2) was observed on Opuntia basilaris, Dudleya arizonica Rose or Agave deserti Engelm. plants, grown either with supplemental irrigation or natural rainfall. In addition, in the field SO(2) had no effect on CO(2) uptake, total sulfur content, transpiration, or tissue acidity in either the light or the dark, or in irrigated vs natural rainfall plots.

Journal Article↗
PubMed1986

Reversible inactivation of the O2-labile hydrogenases from Azotobacter vinelandii and Rhizobium japonicum.

Hydrogenases catalyze the reversible activation of dihydrogen. The hydrogenases from the aerobic, N2-fixing microorganisms Azotobacter vinelandii and Rhizobium japonicum are nickel- and iron-containing dimers that belong to the group of O2-labile enzymes. Exposure of these hydrogenases to O2 results in an irreversible inactivation; therefore, these enzymes are purified anaerobically in a fully active state. We describe in this paper an electron acceptor-requiring and pH-dependent, reversible inactivation of these hydrogenases. These results are the first example of an anaerobic, reversible inactivation of the O2-labile hydrogenases. The reversible inactivation required the presence of an electron acceptor. The rate of inactivation was first-order, with similar rates observed for methylene blue, benzyl viologen, and phenazine-methosulfate. The rate of inactivation was also dependent on the pH. However, increasing the pH of the enzyme in the absence of an electron acceptor did not result in inactivation. Thus, the reversible inactivation was not a result of high pH alone. The inactive enzyme could not be reactivated by H2 or other reductants at high pH. Titration of enzyme inactivated at high pH back to low pH was also ineffective at reactivating the enzyme. However, if reductants were present during this titration, the enzyme could be fully reactivated. The temperature dependence of inactivation yielded an activation energy of 44 kJ X mol-1. Gel filtration chromatography of active and inactive hydrogenase indicated that neither dissociation nor aggregation of the dimer hydrogenase was responsible for this reversible inactivation. We propose a four-state model to describe this reversible inactivation.

Azotobacter↗
PubMed1980

Chemotherapy in pancreatic cancer: results of a controlled, prospective, randomised, multicentre trial.

Forty patients with inoperable pancreatic cancer were included in a prospective, randomised, controlled trial of multiple chemotherapy. The survival of 19 untreated control patients was compared with that of 21 patients who received an initiation course of intravenous fluorouracil, cyclophosphamide, methotrexate, and vincristine given over five days followed by intravenous fluorouracil and mitomycin given over three or five days at six-week intervals thereafter. Median survival in treated patients was 44 weeks, which was significantly longer than the nine weeks seen in controls. In patients without metastases median survival was 48 weeks in the treated group and 12 weeks in controls. In patients with metastases it was 30 weeks in treated patients and seven weeks in controls. The treatment was well tolerated and seemed to confer a significant prolongation of survival, comparing favourably with previous reports of chemotherapy with or without radiotherapy. If the results are confirmed this regimen may be useful in district general hospital practice.

Adult↗
PubMed1979

Chemotherapy in advanced gastric cancer: a controlled, prospective, randomised multi-centre study.

Seventy-six patients with advanced gastric adenocarcinoma were studied in a prospecitive, randmoised, controlled trial using vincristine, methotrexate, cyclophosphamide, and 5-fluorouracil in an initiation course and mitomycin-C with 5-fluorouracil as maintenance therapy. Thirty-seven patients were inoperable and 39 had the primary tumour resected with histological evidence of residual disease. Survival in the inoperable group was short and showed no significant difference between treated and control patients. The median survival times for treated and control groups were 9.5 and 9.0 weeks respectively. In the resected patients there was no difference in ultimate overall survival between the groups but up to 20 weeks there was a suggestion that the probability of survival in treated patients was higher (P = 0.06). The patients were well-matched and it is concluded that chemotherapy has had an early effect but that a further trial with more detailed stratification, particularly of staging and histological grade, is needed. No patient received treatment for longer than two years and unacceptable toxicity occurred in only two patients. Nausea occurred more frequently in the treated group but was short-lived and clinically manageable.

Adenocarcinoma↗
PubMed1976

The neurons in the centromedian-parafascicular complex of the monkey (Macaca mulatta): a Golgi study.

The neurons of the nucleus centrum medianum and the neurons of the nucleus parafascicularis were studied in Golgi preparations of the adult monkey (Macaca mulatta). The cell bodies of the prinicipal neurons in the nucleus centrum medianum have a few somatic spines and vary in shape: some are cubical with protruding angles; some are egg-shaped; some are elongated and sausage-shaped. Four to six slightly branched dendrites of unequal thickness radiate from the cell body. Some dendrites extend for nearly 500 microns; all have dendritic spines. In the nucleus parafascicularis there are two varieties of principal neurons: (1) neurons with somatic spines and (2) neurons without somatic spines. The neurons with somatic spines are most numerous. They have polygonal-shaped cell bodies, prominent somatic spines and processes, larger than spines but considerably smaller than dendrites. These processes bear spines and are designated here "microdendrites." Spines and occasionally a "microdendrite" are found on the axon-hillocks. Five to six dendrites of unequal thickness emerge from the cell bodies. Some extend for more than 500 microns; all have prominent dendritic spines. The neurons without somatic spines are relatively few. Usually three exceptionally long, slightly branched dendrites, one apical and two basal, emerge from their elongated, slim cell bodies. Some dendrites extend for more than 800 microns; all have few scattered spines. The Golgi type II neurons found in both of these intralaminar nuclei have small cell bodies and a few, relatively long, undulating dendrites, which bear bulbous dendritic appendages and beaded axon-like processes. Distally on these dendrites, where the appendages and processes are more numerous, the dendritic appendages and axon-like processes form complex entanglements. Distally on these dendrites, where the appendages and processes are more numerous, the dendritic appendages and axon-like processes form complex entanglements. Beaded axons are found on some but not all of the cell bodies. Morphologically these neurons resemble the local interneurons that have been described in various thalamic nuclei.

Animals↗
PubMed1976

The neurons in the primate subthalamic nucleus: a Golgi and electron microscopic study.

In Golgi preparations of the adult monkey (Macaca mulatta) local interneurons and two varieties of principal neurons, radiating and elongated fusiform, are found in the subthalamic nucleus. The cell bodies of the radiating neurons have a few delicate, somatic spines some of which are occasionally bilobed and trilobed. Five to eight dendritic trunks give rise to branching, tapering dendrites, which may extend for over 400 microns. These dendrites are much thinner than the dendrites in the globus pallidus and the substantia nigra. Some neurons have many and some neurons have few dendritic spines. When numerous the dendritic spines are concentrated on the dendritic trunks and proximal dendrites. The relatively few elongated fusiform neurons are found not only in the capsule but also in the center of the nucleus. Most dendrites emerge from the opposite poles of their smooth surfaced cell bodies. They have a few dendritic spines. Some of these dendrites extend for more than 750 microsn. In 1-micron thick plastic sections lipofuscin granules are present in some but not all principal neuron cell bodies of the monkey (Macaca mulatta); but these granules are present in all principal neuron cell bodies of the pig-tail monkey (Macaca nemestrina) and of the squirrel monkey (Saimiri sciureus). The local interneurons have small cell bodies and a few relatively long undulating dendrites. The dendrites have bulbous dendritic appendages of varying complexity and beaded axon-like processes. The dendritic appendages and axon-like processes are more numerous distally and on the distal ends of the dendrites they form complex entanglements. Axons coming from the cell body have not been observed. The cell bodies of the local interneurons are identified in cresyl violet stained sections of the monkey (Macaca mulatta), in 1-micron thick plastic sections and electron micrographs of the squirrel monkey (Saimiri sciureus). They have relatively large nuclei surrounded by a thin rim of cytoplasm rich in polyribosomes.

Animals↗
PubMed1976

Afferent fibers in the substantia gelatinosa of the adult monkey (Macaca mulatta): a Golgi study.

In horizontally and sagittally sectioned Golgi preparations of the adult monkey spinal cord the afferent fibers in the substantia gelatinosa (laminae II and III of Rexed, '52) were studied with the hope of finding clues that would make it possible to correlate them with the afferent fibers that Ramón y Cajal ('09) traced from the white matter into the substantia gelatinosa in Golgi preparations of the newborn cat. Throughout the substantia gelatinosa there are fibers with fine terminal branches, bearing small "bouton en passant" endings. These fine terminal branches and the collaterals of the axons of the neurons in the substantia gelatinosa are similar; hence, the fine terminal branches are interpreted as the terminals of the proprius bundles generated by the axons of the neurons in the substantia gelatinosa. Also, there are fibers in lamina II that can be followed for relatively long distances (900 microns) before they are cut off in section. They have collaterals bearing large irregular endings, which usually consist of several or more elongated swelling connected by constricted regions. Some of these endings have holes within them and their surfaces have prominent indentations. The fibers with fine terminal branches and the fibers with large irregular endings are interpreted here as the two varieties of fine or superficial collaterals of the substance of Rolando described by Ramóm y Cajal ('09). The most elaborate afferent formations in the present material are found in horizontal sections. They are designated "confined ansiform axonal complexes" and are confined to elongated, oblong blocks of substantia gelatinosa that approximate each other in length, width and depth. Their branches, running rostrally and caudally, loop back and forth, interweave in and intricate pattern and bear large synaptic endings. Because these formations are elaborate and because their parent fibers and initial branches are thicker in lamina III than they are in lamina II, these complexes are interpreted here as the large or deep collaterals of the substance of Rolando described by Ramón y Cajal ('09). Considering their shapes, sizes and surface contours, it is probable that the large endings on the ansiform axonal complexes and the large irregular endings on the long fibers in lamina II are the central terminals in the glomeruli of the substanta gelatinosa that have been revealed by electron microscopy. Finally, there are fine collaterals from fibers in Lissauer's fasciculus which distribute exclusively to the marginal zone (lamina I) of the dorsal horn. Their endings are ovoid or bulbous and are almost uniformly approximately 2 microns in diameter. Undoubtedly, these collaterals are the marginal collaterals Ramón y Cajal ('09) demonstrated in Ehrlich's methylene blue preparations of the 8-day old cat.

Animals↗
PubMed1976

The basilar pontine gray in the adult monkey (Macaca mulatta): a Golgi study.

In Golgi preparations of the adult monkey (Macaca mulatta) two types of neurons are distinguished in the pontine gray: (1) larger neurons which impregnate most frequently and (2) smaller neurons which impregnate rarely. The former are judged to be projection neurons with myelinated axons because only the initial segments of their axons impregnate, while the latter are judged to be intrinsic neurons since they appear to participate only in the local circuitry of the pontine gray. The projection neurons show a variety of sizes and shapes and are the equivalent of the large, medium and small neurons that Ramón y Cajal ('09) illustrated in the pons of the 5-day-old infant. Their cell bodies are rounded, polygonal, triangular, egg-, pear-, and spindle-shaped. Some have somatic spines. Usually four to seven dendrites issue from the cell body and as they branch they attentuate. The dendrites have knobby, nodular protuberances which give them a gnarled appearance. Also the dendrites have a few scattered spines. In most instances the dendrites have a wavy recurring pattern. Neurons pressed against the corticospinal, corticopontine fiber bundles frequently have elongated cell bodies and the dendrites sprouting from them form, tight, brush-like arrays. The intrinsic neurons have small ellipssoid or pear-shaped cell bodies and two or three long dendrites, which do not taper. In some impregnations short axons issuing from the cell body were found and in other impregnations several widely separated, shor axon-like processes were found on dendrites. A striking feature of the intrinsic neurons is the presence of stalked dendritic appendages bearing one or more bulbous bodies, 1 to 3 microns in diameter. The intrinsic neurons in no way resemble the hairy or mossy cells with short axis cylinders that Ramón y Cajal (09) described in the pons of the 5-day-old infant. The latter were not found in the present material.

Animals↗
PubMed1976

Some aspects and implications of coital physiology.

A review of some experiments in human coital physiology in the home setting considers their possible value to the sex therapist. Blood pressure changes are described in normal subjects with reference to their relevance in patients with heart disease or high blood pressure. Respiratory patterns and intravaginal and intrauterine pressure changes are described during coitus, and their significance in different types of female orgasm are discussed. It now appears that a specific deeply satisfying and terminative female orgasm is associated with a particular type of respiratory pattern and intrauterine pressure change. The use of radiotelemetry devices to measure pressure and pH changes during coitus makes home studies possible. Further projects and areas for future study are considered.

Blood Pressure↗
PubMed1976

The striatal efferents in the globus pallidus and in the substantia nigra.

The radial fibers in the globus pallidus are the striatal efferents. Evidence now indicates that they arise from medium-sized neurons in the striatum. During their transit of the globus pallidus, they give off collaterals in both segments of the globus pallidus and undergo reduction in caliber. It has not been possible to observe the same radial fiber emitting collaterals in both segments of the globus pallidus, and the prospects of ever doing so are not good. The radial fibers in the medial segment of the globus pallidus continue into the substantia nigra by way of the "comb" bundle. The divergence and convergence in the striatal efferent systems is considerable. The afferent plexuses of fine fibers bearing bouton en passant endings, which completely ensheath the long dendrites in the globus pallidus and the substantia nigra and make "longitudinal axodendritic connections," are derived from the convergence of branches off the collaterals of a number of different radial fibers in the globus pallidus and the convergence of "comb" bundle fibers in the substantia nigra. The synaptic endings on these fibers constitute most of the endings in the globus pallidus. They are the endings with large, egg-shaped, synaptic vesicles and form symmetrical synapses.

Animals↗
PubMed1975

The radial fibers in the globus pallidus.

In our Golgi collection of adult monkey brains the striatal efferents, i.e., the radial fibers in the globus pallidus and the "comb" bundle fibers in the internal capsule and in the cerebral peduncle, are well impregnated in the horizontally sectioned brain and in a sagittal sectioned brain. Since collaterals emerging from radial fibers are seen only in the horizontal series and not in the saggittal series, the interpretation is that they proceed anteriorly and posteriorly only, following the curvature of the pallidal segments, and do not run superiorly or inferiorly as they emerge. Although radial fibers emitting collaterals in the lateral segment and in the medial segment of the globus pallidus have been observed, it has not been possible to observe the same radial fiber emitting collaterals in both pallidal segments and the prospects of ever doing so are not good. The radial fibers converging in the globus pallidus pursue many radii and there is little coincidence between the plane of section and the planes in which they travel. At most only severed radial fiber segments 100-150 microns in length can be found in the horizontal sections needed to observe the collaterals. Moreover, sagittal sections trodorsally, as they pass through the internal medullary lamina to enter the medial segment of the globus pallidus. The radial fibers in the medial segment of the globus pallidus are continuous with the "comb" bundle fibers and appear to be thinner than the radial fibers in the lateral segment of the globus pallidus. It is not proved; nonetheless, the view expressed here is that the radial fibers are thinner in the medial segment of the globus pallidus because they may be the same fibers that gave off collaterals in the lateral segment of the globus pallidus. This is discussed in the light of the electrophysiological disclosure of Yoshida et al. ('71, '72) that caudatopallidal fibers are collaterals off caudatonigral fibers. The afferent plexuses of fine, "bouton en passage" fibers, which completely ensheath the long radiating dendrites in the globus pallidus (Fox et al., '66) are well impregnated in the horizontal series. Obviously, they are formed by a number of ultimate branches converging from the collateral brances of a number of different radial fibers. The divergence, too, in this system must be considerable; however, its true extent can only be surmised from the several radial fibers and radial fiber collaterals seen in the incompletely impregnanted Golgi section. Continued.

Animals↗
PubMed1975

Computer measurements of axis cylinder diameters of radial fibers and "comb" bundle fibers.

In electron micrographs of the squirrel monkey (Saimiri sciureus) brain in the striatal efferents were observed at two different levels in their course: (1) in cross-sectioned radial fiber bundles just before they enter the globus pallidus; (2) in cross-sectioned "comb" bundle fibers just before they enter the substantia nigra. In the radial bundles nearly all of the fibers are myelinated; in the "comb" bundle most are unmyelinated. The polarity of all the "comb" bundle fibers is descending. None of them degenerate following a large lesion in the substantia nigra but they do degenerate following a large lesion in the striatum. Also following this latter lesion the endings with large synaptic vesicles, which make up most of the endings in the globus pallidus and the substantia nigra, degenerate. For computer measurements, electron micrographs of the radial bundle were enlarged photographically to a final magnification of 20,000; those of the "comb" bundle to times 50,000. Measurements of 1309 radial fibers revealed a mean axis-cylinder diameter of 0.68 microns, and measurements of 749 unmyelinated "comb" bundle fibers gave a mean axis-cylinder diameter of 0.21 microns. Myelinated fibers were not included in the "comb" bundle measurements because it contains myelinated fibers of pallidal origin in addition to myelinated fibers of striatal origin. The results here indicate that the striatal efferents undergo a decided decrease in axis-cylinder diameter during their transit through the globus pallidus. It is suggested that the large non-spine bearing neurons in the striatum are the source of the striatal efferents and that they send their axons into the substantia nigra and enroute spend a great quantity of their axoplasm by extending extensive collaterals in both segments of the globus pallidus. This could account for the decreased caliber of the striatal efferents in the "comb" bundle and other findings in the striatum, globus pallidus and substantia nigra.

Animals↗