Embedment in glycol methacrylate at low temperature allows immunofluorescent localization of a labile tissue protein

The antigenic activity of a labile protein postulated to the hormone ovine chorionic somatomammotropin (OcS) is preserved in tissue fixed in either glutaraldehyde or paraformaldehyde and low temperature-embedded in the water-soluble plastic glycol methacrylate. Immunofluorescence techniques used on 1--2 micrometer thick sections show that this protein is located in the cytoplasm of certain fetal chorionic cells in association with small spherical bodies, which may be lipid. The use of borohydrate reduction or treatment with Schiff's reagent to reduce glutaraldehyde-induced background fluorescence is described.     

Skeletal muscle metabolism in individuals with spinal cord injury

With increasing survival rates in people with spinal cord injuries (SCI), detection and prevention of metabolic and cardiovascular disease have become increasingly important. Few studies have evaluated in vivo mitochondrial function in paralyzed skeletal muscle. The purpose of this study was to compare oxidative muscle metabolism using the rate of phosphocreatine (PCr) resynthesis measured by magnetic resonance spectroscopy (MRS) in people with SCI and able-bodied (AB) controls. Eight subjects with complete SCI (American Spinal Injury Association Impairment Scale A, levels T3-T12, injury duration 2-13 years) were compared with 12 AB controls. T1-weighted (1)H MR images of the thigh were taken to identify skeletal muscle. Phosphorous MRS was performed with a 13 × 13-cm(2) surface coil placed on the right vastus lateralis in a 3 Tesla clinical MRI scanner. PCr resynthesis was measured after electrical stimulation for 60 s at 4 Hz in SCI and AB and in AB subjects after 39 s of voluntary isometric contractions. Resting metabolites were not different between SCI and AB, except for an elevated phosphodiester peak. PCr recovery was slower in AB subjects using electrical stimulation compared with voluntary exercise (28.4 ± 6.1 vs. 41.5 ± 4.3 s; P < 0.05). PCr recovery rates and calculated muscle maximum oxidative capacity in SCI were both 52% of electrically stimulated AB (P < 0.001). In vivo oxidative metabolism was reduced in paralyzed muscle to a similar extent as seen in people with mitochondrial myopathies and heart failure.     

Diet-induced obesity severely impairs myelinated aortic baroreceptor reflex responses

Diet-induced obesity (DIO) attenuates the arterial cardiac baroreceptor reflex, but the mechanisms and sites of action are unknown. This study tested the hypothesis that DIO impairs central aortic baroreceptor pathways. Normal chow control (CON) and high-fat-chow obesity-resistant (OR) and obesity-prone (OP) rats were anesthetized (inactin, 120 mg/kg) and underwent sinoaortic denervation. The central end of the aortic depressor nerve (ADN) was electrically stimulated to generate frequency-dependent baroreflex curves (5-100 Hz) during selective activation of myelinated (A-fiber) or combined (A- and C-fiber) ADN baroreceptors. A mild stimulus (1 V) that activates only A-fiber ADN baroreceptors induced robust, frequency-dependent depressor and bradycardic responses in CON and OR rats, but these responses were completely abolished in OP rats. Maximal activation of A fibers (3 V) elicited frequency-dependent reflexes in all groups, but a dramatic deficit was still present in OP rats. Activation of all ADN baroreceptors (20 V) evoked even larger reflex responses. Depressor responses were nearly identical among groups, but OP rats still exhibited attenuated bradycardia. In separate groups of rats, the reduced heart rate (HR) response to maximal activation of ADN A fibers (3 V) persisted in OP rats following pharmacological blockade of β(1)-adrenergic or muscarinic receptors, suggesting deficits in both parasympathetic nervous system (PNS) and sympathetic nervous system (SNS) reflex pathways. However, the bradycardic responses to direct efferent vagal stimulation were similar among groups. Taken together, our data suggest that DIO severely impairs the central processing of myelinated aortic baroreceptor control of HR, including both PNS and SNS components.     

EARLY SENESCENCE OF CORTICAL CELLS IN THE ROOTS OF CEREALS. HOW GOOD IS THE EVIDENCE?

There are numerous reports that cortical cells senesce in young, otherwise healthy main roots of cereals, including corn. These are based on apparent absence of nuclei in root segments or transverse sections after acridine-orange staining. Senescence is said to progress from the outer to the inner cortex basipetally from the root tip, except cells around branch bases where nuclei always stain. We studied axile roots of soil-grown cereals using various methods to detect nuclei primarily in longitudinal sections. No senescence marked by nuclear loss was found in healthy-looking intact cortices. Cortical cells of mature corn roots remained alive except where aerenchyma developed. No cortical death had occurred in barley, wheat, or oat seminal roots in 15-,17-, and 20-day-old plants, respectively, but cortical cells in older regions of seminal and nodal roots did collapse and slough off, but with no evidence for earlier loss of nuclei. Failure to detect acridine-orange-stained nuclei may not indicate that cells are senescent, and can be an artifact caused by sectioning method and wall impermeability. The effectiveness of other methods for evaluation of root cell vitality is discussed.     

Noninvasive assessment of vascular function in the posterior tibial artery of healthy humans

Flow-mediated dilation (FMD) measures the ability of an artery to relax in response to increases in blood velocity. FMD, primarily of the brachial artery, has been used as a noninvasive method of assessing vascular health. The purpose of this study was to assess FMD in the lower legs of humans. Six healthy subjects (27 PlusMinus; 6 yrs) were tested. Doppler ultrasound images of the posterior tibial artery were taken before, during, and after 5 minutes of proximal cuff occlusion. FMD was measured as the percent increase in diameter after cuff release. Vascular tone was calculated using the resting diameter as a percentage of the vessel's vasoactive range. Minimum diameter occurred during ischemia and maximal diameter occurred following reactive hyperemia with local heating. The lower leg was heated with 10 minutes of immersion in 44 degrees C water. Mean diameters at rest, cuff, and during release were 0.267 PlusMinus; 0.062, 0.162 PlusMinus; 0.036, 0.302 PlusMinus; 0.058 cm, respectively. FMD was 13.5 PlusMinus; 6.6 % and vascular tone was 29 PlusMinus; 16.3%. We also found that retesting on a second day produced mean diameter values within 8% of the first day. Larger resting diameter (decreased tone) correlated with decreased FMD (r2 = 0.73). These results suggest that FMD and vascular tone can be measured in the posterior tibial artery. This is a potentially powerful tool to non-invasively measure vascular health in the lower legs of people at risk for vascular disease.     

Blood flow response to a postural challenge in older men and women

BACKGROUND: The purpose of this study was to measure blood flow in the carotid and femoral arteries, heart rate and blood pressure in response to postural challenge in older adults. A second purpose was to determine if older men and women have different cardiovascular responses to a postural challenge such as tilt. METHODS: Thirty-seven healthy elderly men and women participated in this study (69-82 years old). All subjects had similar physical activity levels. Postural challenge was induced by a 60 degrees tilt at the level of the waist. Continuous carotid blood flow and femoral blood flow was measured with Doppler ultrasound. RESULTS: Carotid blood flow was significantly reduced 17% in both men and women immediately after tilt (p < 0.001), and by 3.2% two minutes after tilt (p < 0.001). Femoral blood flow decreased 59.4% in men and 61% in women immediately after tilt (p < 0.001), and remained significantly decreased two minutes after tilt by 21% (p <0.001). Heart rate increased by 15% in men (p < 0.001), and 26% in women immediately after the tilt (p < 0.001). Heart rate returned to resting values within two minutes in both men and women. Response to tilt was not significantly related to self-report physical activity levels or to six-minute walk time. CONCLUSION: A postural challenge induced larger changes in the femoral artery compared to the carotid artery. There were no differences between men and women to a tilt table test except for differences in heart rate response. There was no difference in the blood flow responses to postural challenge with physical activity level or between healthy older men and women.     

Genomic affinities in Arachis section Arachis (Fabaceae): molecular and cytogenetic evidence

Section Arachis is the largest of nine sections in the genus Arachis and includes domesticated peanut, A. hypogaea L. Most species are diploids (x=10) with two tetraploids and a few aneuploids. Three genome types have been recognized in this section (A, B and D), but the genomes are not well characterized and relationships of several newly described species are uncertain. To clarify genomic relationships in section Arachis, cytogenetic information and molecular data from amplified fragment length polymorphism (AFLP) and the trnT-F plastid region were used to provide an additional insight into genome composition and species relationships. Cytogenetic information supports earlier observations on genome types of A. cruziana, A. herzogii, A. kempff-mercadoi and A. kuhlmannii but was inconclusive about the genome composition of A. benensis, A. hoehnei, A. ipaensis, A. palustris, A. praecox and A. williamsii. An AFLP dendrogram resolved species into four major clusters and showed A. hypogaea grouping closely with A. ipaensis and A. williamsii. Sequence data of the trnT-F region provided genome-specific information and showed for the first time that the B and D genomes are more closely related to each other than to the A genome. Integration of information from cytogenetics and biparentally and maternally inherited genomic regions show promise in understanding genome types and relationships in Arachis.     

The time course of the induction of callose in wounded pea roots

Summary Initial study indicated that much callose is produced in pea root tissues during the preparation of fresh hand-cut sections or during conventional fixation in formalin-acetic acid-alcohol, glutaraldehyde or acrolein. In contrast, there is little callose in freeze-substituted tissues and this is mostly in sieve tubes and considered endogenous. Freeze-substitution was subsequently used to monitor wound-induced callose development in the various tissues of pea roots. This development was fastest in the phloem, first detected 1 minute post-wounding and complete by 3 hours. In some parenchyma cells full development was delayed by 20 hours. By 100 hours, wound callose was no longer detectable in parenchyma cells but remained undiminished in the phloem. The implications of these results for all studies involving callose localization are discussed.Abbreviations C callose - FAA formalin-acetic acid-alcohol - GMA glycol methacrylate - P phloem - PAS periodic acid-Schiffs - PF phloem fibres - PP pith parenchyma - PW post-wounding