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Biomedical subjects

W K Smith

Publications and source records attributed to W K Smith.

At least 37 records · Page 2Linked to original sources
PubMed1993

Simulated influence of leaf geometry on sunlight interception and photosynthesis in conifer needles.

The light interception capabilities of individual conifer needles are governed by their cross-sectional geometry and their orientation to sunlight. Leaf cross sections typical of conifer tree species were modeled to quantify the interception of direct sunlight over a range of incident light angles. The needle shapes exhibited by Abies nordmanniana Spach, Picea asperata Master, Pinus cembra L., P. monophylla Torr & Frém., and P. sylvestris L. were selected because they are representative of the range of geometric shapes found in conifer tree species. Calculated light interception values were compared to corresponding predictions for a laminar broadleaf. Estimates of carbon gain were derived from computed incident light integrated over the leaf cross section and a representative curve of conifer photosynthetic response to light. Flat leaf cross sections (e.g., Abies nordmanniana) with high surface area to volume ratios (> 6) intercepted more light per unit area at high angles of incidence than thick leaves. Thick leaves (e.g., Pinus cembra) intercepted more light at low angles of incidence than at high angles of incidence. Needles of Pinus monophylla had no angular dependence for light interception because of their circular cross section. Large differences in estimated CO(2) assimilation occurred among the species, especially when CO(2) uptake was expressed on a unit volume basis. A maximum uptake of 67.9 mmol CO(2) m(-3) s(-1) was predicted for A. nordmanniana compared to a minimum of 39.7 mmol m(-3) s(-1) for P. monophylla. A greater angular dependence occurred for estimates of CO(2) uptake than for estimates of light interception.

Journal Article↗
PubMed1992

Disease-specific patterns of locus coeruleus cell loss.

Computer visualization techniques were used to map and to quantitatively reconstruct the entire locus coeruleus, including the nucleus subcoeruleus, to compare the topographic patterns of cell loss in postmortem brains from patients with Parkinson's disease, Alzheimer's disease, and Down syndrome. There was comparable cell loss in all three diseases (approximately 60%) compared with aged normal subjects, and there was a significant loss of nucleus subcoeruleus cells specifically in patients with Parkinson's disease (63%). There was a significant positive correlation between the magnitude of locus coeruleus cell loss and the duration of Alzheimer's disease, but no such correlation was found for Parkinson's disease. In patients with Parkinson's disease, there was comparable cell loss throughout the rostral-caudal extent of the nucleus; however, in patients with Alzheimer's disease and Down syndrome, the greatest cell loss always occurred within the rostral portion of the nucleus, with a relative sparing of caudal cells. These data are consistent with the hypothesis that cell loss in Parkinson's disease is the result of a pathological process that attacks the catecholaminergic cells of the locus coeruleus and the subcoeruleus in general; in Alzheimer's disease and Down syndrome, however, the pathological process only affects the rostral, cortical-projecting locus coeruleus cells and spares the caudal, noncortical-projecting cells.

Aged↗
PubMed1992

Analgesic efficacy of bromfenac, ibuprofen, and aspirin in postoperative oral surgery pain.

We recently demonstrated that 25 mg of bromfenac, a new nonsteroidal anti-inflammatory analgesic, is at least as effective as 400 mg of ibuprofen in relieving postoperative oral surgery pain. Our objective in this study was to determine whether higher doses were significantly more effective. Two hundred eighty (280) outpatients with postoperative pain after the surgical removal of impacted third molars were randomly assigned, on a double-blind basis, a single oral dose of 10, 25, 50, or 100 mg bromfenac; 650 mg aspirin; 400 mg ibuprofen; or placebo. Subjects rated their pain and its relief for 8 hours. All active treatments were significantly superior to placebo, and bromfenac and ibuprofen were significantly superior to aspirin. The slope of the dose-response curve of bromfenac was significant. The 100 mg bromfenac dose was significantly more effective than the 400 mg ibuprofen dose and had a significantly longer duration of analgesic action.

Aspirin↗
PubMed1991

Effect of caffeine on ibuprofen analgesia in postoperative oral surgery pain.

Recent studies have demonstrated that caffeine acts as an analgesic adjuvant when combined with acetaminophen, aspirin, or their mixture. Our objective was to determine whether similar enhancement of analgesia could be demonstrated when caffeine is combined with ibuprofen. On a double-blind basis, a single oral dose of ibuprofen (50, 100, or 200 mg), a combination of ibuprofen, 100 mg, with caffeine, 100 mg, a combination of ibuprofen, 200 mg, with caffeine, 100 mg, or placebo was randomly assigned to 298 outpatients with postoperative pain after the surgical removal of impacted third molars. With a self-rating record, subjects rated their pain and its relief hourly for 8 hours. All active treatments were significantly superior to placebo, and the caffeine effect was significant for every measure of analgesia. Relative potency estimates indicated that the combination was 2.4 to 2.8 times as potent as ibuprofen alone. The combination also had a more rapid onset and longer duration of analgesic action. The analgesic adjuvancy of caffeine clearly extends to combinations with nonsteroidal anti-inflammatory drugs other than acetaminophen or aspirin.

Adolescent↗
PubMed1991

Photosynthesis, water relations and mortality in Abies lasiocarpa seedlings during natural establishment.

Few studies have investigated the ecophysiology of natural seedling establishment in forest trees not associated with anthropogenic disturbance. Photosynthesis and water relations measurements were made on one- through four-year-old seedlings of Abies lasiocarpa Nutt. (subalpine fir) establishing naturally in an understory environment. First (current)-year seedlings generally had only cotyledons, whereas most second-year seedlings had both cotyledons and primary leaves. Mortality was high (> 60%) in first-year seedlings with the greatest mortality (> 90%) measured at the more open, sun-exposed sites within the understory. Seedling mortality was negligible after the first year of growth at shaded microsites and after the second year of growth at sunny microsites. Photosynthetic CO(2) uptake at light saturation was considerably lower in first-year than in fourth-year seedlings (0.6 micromol m(-2) s(-1) versus 1.7 micromol m(-2) s(-1)) and occurred at lower solar irradiance (240 micromol m(-2) s(-1) versus 600 micromol m(-2) s(-1) of photosynthetically active radiation). Differences in photosynthetic capacity were due to differences in both stomatal and non-stomatal limitations to CO(2) uptake. Carbon dioxide assimilation in first- and second-year seedlings was 28 and 29%, respectively, of the mean value measured for fourth-year seedlings. Although first-year seedlings had low transpiration rates, their water use efficiency (photosynthesis/transpiration) was less than half that of fourth-year seedlings and their water potentials were lower than those of all other age classes (0.46 mol CO(2) mmol(-1) H(2)O and -3.0 MPa, respectively). The stomatal limitation to CO(2) uptake was approximately 21% in first- and second-year seedlings, and increased to 39% in fourth-year seedlings. Intercellular CO(2) concentrations were greater in first- and second-year seedlings (255 and 250 microl l(-1), respectively) than in third- and fourth-year seedlings (203 and 186 microl l(-1), respectively). Thus, abrupt increases in water status and photosynthetic capacity after the first or second year of growth appear crucial for survival to maturity. Moreover, differences in temperature and water relations according to microsite may be major factors determining seedling establishment and, thus, the distributional and successional patterns observed for adult trees of Abies lasiocarpa.

Journal Article↗
PubMed1991

Importance of the method of leaf area measurement to the interpretation of gas exchange of complex shoots.

Net CO(2) uptake in full sunlight, total leaf area (TLA), projected leaf area of detached leaves (PLA), and the silhouette area of attached leaves in their natural orientation to the sun at midday on June 1 (SLA) were measured for sun shoots of six conifer species. Among species, TLA/SLA ranged between 5.2 and 10.0 (x bar = 7.3), TLA/PLA ranged between 2.5 and 2.9 (x bar = 2.7) and PLA/SLA ranged between 2.0 and 3.7 (x bar = 2.2). These ratios were reflected in the ratios of net photosynthesis computed on the basis of the three measures of leaf area. The much smaller values for TLA/PLA compared with the values for TLA/SLA indicate that leaf orientation effects, or shading, or both, caused more variation in the interception of solar radiation than did variation in leaf geometry (i.e., cross-section). Silhouette leaf area of lodgepole pine, (Pinus contorta spp. latifolia) and subalpine fir (Abies lasiocarpa) shoots measured at the summer solstice varied almost 2-fold with diurnal changes in solar altitude and azimuth. Sun shoots of both species and shade shoots of lodgepole pine had the greatest SLA during the early morning and late afternoon. The midday decline in SLA was related to the relatively upright orientation of needles of subalpine fir sun shoots and the relatively upright orientation of both sun and shade shoots of lodgepole pine. Shade shoots of subalpine fir reached a maximum in SLA at midday and this was related to the near horizontal orientation both of the shoots and the needles on them.

Journal Article↗
PubMed1990

Evaluation of aspirin, caffeine, and their combination in postoperative oral surgery pain.

Three hundred fifty outpatients with postoperative pain after the surgical removal of impacted third molars were randomly assigned, on a double-blind basis, to receive a single oral dose of aspirin 650 or 1000 mg, caffeine 65 mg, a combination of aspirin 650 mg with caffeine 65 mg, or placebo. Using a self-rating record, subjects rated their pain and its relief hourly for 6 hours after medicating. Estimates of summed pain intensity difference, peak pain intensity difference, total relief, peak relief, and hours of 50% relief were derived from these subjective reports. All active treatments except caffeine were significantly superior to placebo. Pairwise comparisons indicated the aspirin-caffeine combination was statistically superior to aspirin 650 mg alone for hours of 50% relief among patients who had severe baseline pain. Adverse effects were transitory and none were serious.

Administration, Oral↗
PubMed1989

Computer-assisted three-dimensional reconstructions of [14C]-2-deoxy-D-glucose metabolism in cat lumbosacral spinal cord following cutaneous stimulation of the hindfoot.

We report on computer-assisted three-dimensional reconstruction of spinal cord activity associated with stimulation of the plantar cushion (PC) as revealed by [14C]-2-deoxy-D-glucose (2-DG) serial autoradiographs. Moderate PC stimulation in cats elicits a reflex phasic plantar flexion of the toes. Four cats were chronically spinalized at about T6 under barbiturate anesthesia. Four to 11 days later, the cats were injected (i.v.) with 2-DG (100 microCi/kg) and the PC was electrically stimulated with needle electrodes at 2-5 times threshold for eliciting a reflex. Following stimulation, the spinal cord was processed for autoradiography. Subsequently, autoradiographs, representing approximately 8-18 mm from spinal segments L6-S1, were digitized for computer analysis and 3-D reconstruction. Several strategies of analysis were employed: 1) Three-dimensional volume images were color-coded to represent different levels of functional activity. 2) On the reconstructed volumes, "virtual" sections were made in the horizontal, sagittal, and transverse planes to view regions of 2-DG activity. 3) In addition, we were able to sample different regions within the grey and white matter semi-quantitatively (i.e., pixel intensity) from section to section to reveal differences between ipsi- and contralateral activity, as well as possible variation between sections. These analyses revealed 2-DG activity associated with moderate PC stimulation, not only in the ipsilateral dorsal horn as we had previously demonstrated, but also in both the ipsilateral and contralateral ventral horns, as well as in the intermediate grey matter. The use of novel computer analysis techniques--combined with an unanesthetized preparation--enabled us to demonstrate that the increased metabolic activity in the lumbosacral spinal cord associated with PC stimulation was much more extensive than had heretofore been observed.

Animals↗
PubMed1989

1-Methyl-4-(2'-methylphenyl)-1,2,3,6-tetrahydropyridine (2'CH3-MPTP)-induced degeneration of mesostriatal dopaminergic neurons in the mouse: biochemical and neuroanatomical studies.

The neurotoxic effects of 1-methyl-4-(2'-methylphenyl)-1,2,3,6-tetrahydropyridine (2'CH3-MPTP), a substituted analog of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, were studied in BALB/cJ mice. Moderate doses of 2'CH3-MPTP produced a greater depletion of dopamine (DA) in the striatum (45%) than in the nucleus accumbens (23%), and in these same animals, there was a 35% loss of midbrain DA neurons. The greatest loss of DA cells occurred within the substantia nigra (43%), and there was also a significant loss of cells within the ventral tegmental area (28%). Higher doses of 2'CH3-MPTP decreased levels of DA more in the axon terminal/forebrain region (72%) than in the cell body/midbrain region (25%). Similar forebrain/midbrain DA depletion ratios were also found in mice that received an electrolytic lesion of the midbrain DA neurons; there was a greater Da depletion in the forebrain (29%) than in the midbrain (8%). In both 2'CH3-MPTP and electrolytically lesioned animals there was a significant increase in DA turnover in the forebrain region, as measured by the homovanillic acid/DA ratio. These data indicate that 2'CH3-MPTP: (1) destroys DA neurons within two midbrain regions containing cells which project to the striatum (i.e. mesostriatal DA neurons), rather than just nigrostriatal DA neurons; (2) produces a greater loss of DA in the axon terminal region than in the cell body region; and (3) influences the mesostriatal DA neurons in the same way as does a lesion to the cell bodies. These data are discussed with regard to the pathophysiology of 2'CH3-MPTP.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1989

Midbrain dopaminergic cell loss in Parkinson's disease: computer visualization.

Computer visualization techniques were used to map the distribution of dopaminergic neurons within midbrain tissue sections from 5 parkinsonian patients and 3 age-matched control subjects. The Parkinsonian brains had over 50% fewer dopaminergic neurons within the midbrain than age-matched normal brains. The cell loss occurred within the combined substantia nigra (dopaminergic nucleus A9) and retrorubral (dopaminergic nucleus A8) areas (greater than 61%) and the ventral tegmental area (dopaminergic nucleus A10) (greater than 42%). The cell loss was greatest within the ventral portion of the substantia nigra zona compacta. The specific pattern of cell loss is very similar to the pattern of cells that project to the striatum (as opposed to cortical and limbic sites) in animal neuroanatomical tracing experiments. These data suggest that Parkinson's disease preferentially destroys midbrain dopaminergic neurons in nuclei A8, A9, and A10, which project to the striatum.

Aged↗
PubMed1988

The human locus coeruleus: computer reconstruction of cellular distribution.

Quantitative neuroanatomical techniques were developed to map the distribution of norepinephrine-containing locus coeruleus (LC) neurons in the adult human brain. These neurons reside in the dorsolateral pontine tegmentum and are identifiable by their neuromelanin pigment content. Five brains, ranging in age from 60 to 104 years, were examined. Outlines of coronal or sagittal sections containing the LC were entered into a computer along with the location of each cell, certain neuroanatomical landmarks, and cell size. Sections were aligned with specific neuroanatomical landmarks so that the computer-generated distribution of cells was representative of the in situ distribution of cells. Analysis of (1) the number of cells in sections throughout the rostrocaudal extent of the nucleus, (2) cell size, (3) 3-dimensional reconstructions of the distribution of cells within the brain stem, and (4) 2-dimensional cell-frequency maps, make it possible to quantitatively characterize the distribution of cells within this large nucleus. The total estimated number of LC cells on both sides of the brain ranged from 45,562 to 18,940 (youngest to oldest), and mean soma area ranged from 835 to 718 micron 2 (youngest to oldest). The nucleus is "tube-like" in shape, has a rostrocaudal extent of approximately 16 mm, and is bilaterally symmetrical. Two-dimensional cell-frequency maps were developed to illustrate the regional distribution of cell frequencies at any rostrocaudal/mediolateral point on the horizontal plane; the total unilateral area of the LC ranged from 32.8 to 17.2 mm2 (youngest to oldest). The techniques developed to characterize the 2- and 3-dimensional distributions of LC neurons can be used in future studies to quantitatively examine the effects of aging and disease on this and other brain nuclei.

Cell Count↗
PubMed1987

The stress analogy.

The author calls attention to the advantages of using the engineering meaning of stress and strain when applying these terms to describe the effects of social and physical forces on people. Such an analogy opens up the possibility of measuring the amount of damage from excess stresses existing in people, as well as estimating their limits and remaining strengths. It also explains why some people are more affected by a given stressor than other people.

General Adaptation Syndrome↗
PubMed1985

Rat medulla oblongata. IV. Topographical distribution of catecholaminergic neurons with quantitative three-dimensional computer reconstruction.

We examined serial 40 micron vibratome, immunoperoxidase-stained sections of the medulla with tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH), and phenylethanolamine N-methyltransferase (PNMT) antisera followed by Nissl staining to locate catecholaminergic neurons in cytoarchitectonic regions followed by a three-dimensional (3D) computer reconstruction of these cell groups to determine their spatial organization. Overlay drawings of low and high power photomicrographs showing cell bodies and nuclear boundaries were entered into a digital computer storage system. Every section in the series was plotted to yield an accurate representation of regional densities of cells and location of nuclei, as revealed by two-dimensional plots of individual sections as well as three-dimensional plots of groups of sections. Data files were scanned in a number of ways to obtain total cell counts of TH-, DBH-, and PNMT-immunoreactive cells within a designated area or cell counts of only one type of immunoreactive cell. This combination of data manipulation produced the following results: (1) A1 group is a homogeneous population of noradrenergic neurons at levels caudal to the obex, and at the obex it is mixed with adrenergic cells. The dimensions of the A1 cell group are 1.3 X 2.7 mm, extending from -2.5 to +0.2. Part of this cell group lies in the lateral reticular nucleus. (2) A2 group is not purely noradrenergic as previously suspected. It is a very mixed cell group containing mainly dopaminergic neurons in the area postrema (periventricular region) and the dorsal motor nucleus of the vagus, mainly noradrenergic neurons in the medial subnucleus of the nucleus of the tractus solitarius (nTS), mainly adrenergic neurons in the dorsal strip and dorsal subnucleus of the nucleus of the tractus solitarius, and a mixture of all three catecholaminergic neurons in the other subnuclei of the nTS. The dimensions of this group are 0.4 X 3 mm extending from -2.7 to +0.3. (3) C1 group is a homogeneous population of adrenaline cells extending from +1 to +2.5 with dimensions of 1.5 X 1.5 mm and consisting of scattered neurons some of which occupy the gigantocellular reticular nucleus. (4) C2 group is a homogeneous population of adrenaline neurons extending from +1 to +3 with dimensions of 2.5 X 3 mm. Accurate visual imaging and quantitation of the spatial organization of medullary catecholaminergic neurons within the classical anatomical framework of cytoarchitecture provides an enhanced comprehension of the organization of this region of the central nervous system.

Animals↗
PubMed1985

A renal countercurrent system in marine elasmobranch fish: a computer-assisted reconstruction.

Computer-aided techniques were used to reconstruct the complex renal tubular system in the dorsal kidney region of a marine elasmobranch fish, the little skate (Raja erinacea), from a series of light micrographs of serial sections. It was established that five individual segments of one nephron, consisting of two loops and a distal tubule, are arranged in parallel within an elongated closed tissue sac. Capillaries, which form a network around these nephron segments, enter and exit this sac at the same end. This anatomical arrangement suggests that a complex renal countercurrent multiplier system may be important in fluid regulation in these fish.

Animals↗
PubMed1985

Mucosal nerves and smooth muscle relationships with gastric glands of the opossum: an ultrastructural and three-dimensional reconstruction study.

The precise anatomical relation by which autonomic nerve endings contact gastric epithelial cells to enhance the rate of gastric secretions is not fully understood. The aim of the present study was to clarify this issue by using the technique of serial section reconstruction of areas of the gastric mucosa. The work also explored the possibility of a functional role for a system of smooth muscle strands in the gastric mucosa that emanate from the muscularis mucosa, run in the lamina propria, and are associated in a unique manner with the gastric glands. Electron microscopic serial sections of the gastric mucosa were performed to visualize the entire limiting membrane of gastric epithelial cells to determine any nerve associations (especially varicose endings) with these cells. Evaluation of serial sections of five separate parietal cells showed that their basal membrane did not come in close contact (nearest distance 500 nm) with any nerve axon or varicosity. Moreover, the axons passing in the area of these cells ultimately showed varicose endings associated with smooth muscle cells in the adjacent connective tissue (often separated by only 20 nm), with mast cells or with vascular elements. Additionally, the lateral membrane of these five parietal cells did not contact any endocrine cell in the epithelium, although other parietal cells in the area were adjacent to endocrine cells. Chief cells in the immediate area also did not form any close associations with nerve varicosities. Random analysis of 5,000 additional epithelial cells in these sections showed no close associations to nerve elements with significant accumulations of neurosecretory vesicles (varicosities). Because of the observed existence of innervation to the smooth muscle strands in the area of the gastric glands, serial 1-micron epoxy sections of the gastric mucosa were prepared, and profiles of smooth muscle and gastric glands were entered into a computer-assisted reconstruction system. Three-dimensional reconstruction techniques were employed to reveal the existence of a unique association between the mucosal smooth muscle strands and the gastric glands. The muscle strands arose from the muscularis mucosa at regular intervals and became branched to form an intricate wrap around a series of gastric glands that empty into one gastric pit.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Transfusion-acquired cytomegalovirus infection in cardiac surgery patients.

The incidence of transfusion-acquired primary cytomegalovirus (CMV) infection was studied in 483 cardiac surgery patients. Ninety-six patients (20%) were found to lack antibody to CMV [CMV Ab(-)] as measured by radioimmunoassay. Sixty-eight CMV Ab(-) were followed by viral culture and/or serology from eight weeks to one year after transfusion. Transfusion requirements in CMV Ab(-) patients were as follows: whole blood/packed red blood cells, mean 4.7 +/- 2.6 units; platelets (20 patients), 6.9 +/- 3.8 units; fresh frozen plasma (25 patients), mean 3.3 +/- 1.6 units. Forty-nine percent of 235 donor units tested had antibody to CMV. One donor unit (0.4%) had CMV-specific IgM. This was not associated with CMV infection in the recipient. One patient (1.5%) demonstrated evidence of seroconversion to CMV during the follow-up period. This is significantly less than reported in previously published studies (P less than .01). Serological methods used, the age of the transfused blood, the immune status of the transfusion recipient, and the administration of passive antibody in fresh frozen plasma are factors that may be responsible for the low incidence observed.

Antibodies, Viral↗