Comparative Physiological Studies Research Articles

Phenotypic responses of wild barley to experimentally imposed water stress

Responses to water stress within a population of wild barley from Tabigha, Israel, were examined. The population's distribution spans two soil types: Terra Rossa (TR) and Basalt (B). Seeds were collected from plants along a 100 m transect; 24 genotypes were sampled from TR and 28 from B. Due to different soil water-holding capacities, plants growing on TR naturally experience more intense drought than plants growing on B. In a glasshouse experiment, water was withheld from plants for two periods (10 d and 14 d) after flag leaf emergence. A total of 15 agronomic, morphological, developmental, and fertility related traits were examined by analysis of variance (ANOVA). Ten of these traits were significantly affected by the treatment. A high degree of phenotypic variation was found in the population with significant genotypextreatment and soil typextreatment interactions. Principal component analysis (PCA) was performed using combined control and stress treatment data sets. The first three principal components (pc) explained 88.8% of the variation existing in the population with pc1 (47.9%) comprising yield-related and morphological traits, pc2 (22.9%) developmental characteristics and pc3 (18.0%) fertility-related traits. The relative performance of individual genotypes was determined and water stress tolerant genotypes identified. TR genotypes were significantly less affected by the imposed water stress than B genotypes. Moreover, TR genotypes showed accelerated development under water deficit conditions. Data indicate that specific genotypes demonstrating differential responses may be useful for comparative physiological studies, and that TR genotypes exhibiting yield stability may have value for breeding barley better adapted to drought.

Six opsins from the butterfly Papilio glaucus: molecular phylogenetic evidence for paralogous origins of red-sensitive visual pigments in insects.

It has been hypothesized that the UV-, blue-, and green-sensitive visual pigments of insects were present in the common ancestor of crustaceans and insects, whereas red-sensitive visual pigments evolved later as a result of convergent evolution. This hypothesis is examined with respect to the placement of six opsins from the swallowtail butterfly Papilio glaucus (PglRh1-6) in relationship to 46 other insect, crustacean, and chelicerate opsin sequences. All basal relationships established with maximum parsimony analysis except two are present in the distance and maximum likelihood analyses. In all analyses, the six P. glaucus opsins fall into three well-supported clades, comprised, respectively, of ultraviolet (UV), blue, and long-wavelength (LW) pigments, which appear to predate the radiation of the insects. Lepidopteran green- and red-sensitive visual pigments form a monophyletic clade, which lends support to the hypothesis from comparative physiological studies that red-sensitive visual pigments in insects have paralogous origins. Polymorphic amino acid sites (180, 197, 277, 285, 308), which are essential for generating the spectral diversity among the vertebrate red- and green-sensitive pigments are notably invariant in the Papilio red- and green-sensitive pigments. Other major tuning sites must be sought to explain the spectral diversification among these and other insect visual pigments.

Comparative physiological study of arbutamine with exercise in humans

Comparative physiological study of arbutamine with exercise in humans

Comparative physiological study of arbutamine with exercise in humans

Pharmacological stress testing may be used in the diagnosis of coronary artery disease when there are contra-indications to the use of conventional exercise protocols. The responses to such testing using arbutamine and to conventional treadmill exercise were compared in eight patients. Respiratory gas analysis and cardiovascular observations were performed during both tests. For an equivalent increment in heart rate, both protocols increased systolic blood pressure and serum lactate. Minute ventilation and oxygen consumption also rose during both protocols, but much more so with exercise. The end-tidal partial pressure of CO(2) [35.1 (S.D. 3. 1) to 30.8 (6.6) mmHg] and the dead space/tidal volume ratio (V(D)/V(T)) [0.37 (0.09) to 0.33 (0.08)] fell significantly during arbutamine infusion, but the respiratory exchange ratio did not change during either protocol. Oxygen pulse, a marker of stroke volume, did not change significantly after arbutamine, but rose markedly after exercise [arbutamine, 3.9 (1.1) to 3.37 (0.7) ml. min(-1).beat(-1); exercise, 4.7 (1.4) to 16.1 (4.6) ml.min(-1). beat(-1) (P<0.0001 compared with baseline); difference between peak responses: P<0.0001]. We conclude that arbutamine simulates some of the physiological responses to exercise, although a number of these responses are less marked than during conventional exercise, in particular cardiac output (oxygen pulse). An increase in ventilation is produced, possibly due to direct stimulation of arterial chemoreceptors. These data suggest that the main action of arbutamine is to increase central drive rather than to establish peripheral demand.

ASYMPTOTIC HEIGHT AS A PREDICTOR OF PHOTOSYNTHETIC CHARACTERISTICS IN MALAYSIAN RAIN FOREST TREES

Comparative studies of photosynthetic physiology in rain forest trees have focused on differences related to successional status, with the general finding that early-successional species tend to show physiological characteristics of sun plants, while late-successional species show shade-plant characteristics. The present study examines analogous evolutionary responses to vertical gradients in light availability, through an analysis of patterns of photosynthetic variation among late-successional tropical tree species that differ in adult stature. Larger statured tree species are expected to have higher values for light-saturated photosynthetic rate (Amax) as adults, due to the inevitable gradient in light availability through the canopy. However, we argue that larger statured species should also show a higher Amax, and other “sun-plant” characteristics, as saplings under relatively uniform low light conditions in the forest understory. This prediction follows if the potential for photosynthetic acclimation is finite, and if developmental processes that determine adult-phase physiology also affect the physiology of sapling leaves. We examined relationships between photosynthetic parameters and tree species’ stature using comparative data on 28 late-successional species at Pasoh Forest Reserve, West Malaysia. Species chosen for study represent four genera that each include taxa ranging in size from understory treelets to canopy-level trees, thus enabling “phylogenetically corrected” analyses and stronger inference that observed patterns reflect evolutionary convergence. Amax of understory saplings, as measured on a leaf area, mass, or nitrogen basis, was positively correlated with asymptotic height (Hmax) reached by mature trees of a given species. These relationships were similar in each of the four main study genera, thus supporting the hypothesis of an evolutionary response in photosynthetic characteristics to the vertical gradient in light availability through the canopy. Understory species also commonly exhibited higher leaf-level photosynthetic rates at low light levels than did canopy species within a given genus; however, such “crosses” in photosynthetic light response curves were only pronounced when photosynthesis was expressed on a leaf mass basis. Midcanopy leaves from adult trees displayed Amax(area) values similar to leaves from understory saplings of a given species, while Amax(mass) values for adult trees were lower than those of saplings. This pattern corresponded to lower values for specific leaf area in adult trees than in saplings, a difference that was systematically greater in larger statured species. In sum, a range of both adult tree and sapling physiological parameters, including photosynthetic capacity, light saturation point, and leaf nitrogen content, may be predicted as a function of asymptotic species height. Previous research on vertical gradients in photosynthetic characteristics of forest trees has focused on proximate mechanisms, such as light acclimation responses and nutrient reallocation within individual tree canopies. The present study documents evolved differences among species that also contribute to the overall pattern of photosynthetic variation within forest canopies. Our results suggest that much of the variation in leaf-level physiology among late-successional tropical trees is related to an evolved sun–shade trade-off that corresponds to differences in size among species.

Expression and targeting to the plasma membrane of xClC-K, a chloride channel specifically expressed in distinct tubule segments of Xenopus laevis kidney

ClC-K channels are Cl- channels specifically expressed in vertebrate kidneys. Although their heterologous functional expression is still controversial, indirect evidence points to them as major factors involved in Cl- reabsorption in the nephron. We cloned xClC-K, an amphibian (Xenopus) homologue of mammalian ClC-K. The cDNA encodes a 77 kDa protein presenting 62% similarity with human ClC-Kb. The protein is monoglycosylated and is expressed primarily in the Xenopus kidney. It is localized in the basolateral membranes of proximal convoluted tubules of the nephron and in the apical region of the diluting segments. Heterologous expression of xClC-K in HEK-293 cells showed that the full-length protein is glycosylated and targeted to the cell membrane, but no associated Cl- current could be observed with the patch-clamp recording technique. N-glycosylation of both the native kidney channel and the recombinant protein expressed in HEK-293 conferred on them anomalous behaviour in denaturing PAGE, which is indicative of strong interactions at the extracellular side of the plasma membrane. The expression of ClC-K channels in both mesonephric and metanephric kidneys will permit further comparative physiological studies of Cl- permeabilities at the molecular level.

Expression and targeting to the plasma membrane of xClC-K, a chloride channel specifically expressed in distinct tubule segments of Xenopus laevis kidney

ClC-K channels are Cl- channels specifically expressed in vertebrate kidneys. Although their heterologous functional expression is still controversial, indirect evidence points to them as major factors involved in Cl- reabsorption in the nephron. We cloned xClC-K, an amphibian (Xenopus) homologue of mammalian ClC-K. The cDNA encodes a 77 kDa protein presenting 62% similarity with human ClC-Kb. The protein is monoglycosylated and is expressed primarily in the Xenopus kidney. It is localized in the basolateral membranes of proximal convoluted tubules of the nephron and in the apical region of the diluting segments. Heterologous expression of xClC-K in HEK-293 cells showed that the full-length protein is glycosylated and targeted to the cell membrane, but no associated Cl- current could be observed with the patch-clamp recording technique. N-glycosylation of both the native kidney channel and the recombinant protein expressed in HEK-293 conferred on them anomalous behaviour in denaturing PAGE, which is indicative of strong interactions at the extracellular side of the plasma membrane. The expression of ClC-K channels in both mesonephric and metanephric kidneys will permit further comparative physiological studies of Cl- permeabilities at the molecular level.

Evaluation of sole nitrogen sources for shoot and leaf disc cultures of sugarbeet

Use of single nitrogen sources in nutrient media is essential to ascertaining the relative role and regulation of nitrogen assimilatory steps, and may help identify and understand highly productive media for micropropagation and adventitious shoot formation. Eight endogenous nitrogen-containing ions or compounds in sugarbeet (nitrate, ammonium, glutamine, glutamate, urea, proline, glycine betaine and choline) were examined for ability to serve as sole nitrogen source for shoot or leaf disc culture of sugarbeet (Beta vulgaris L.) model clone REL-1. The most productive concentrations of nitrate, ammonium, urea, and glutamine as sole nitrogen sources were moderately supportive of shoot multiplication (64, 70, 81 and 71%, respectively) and fresh weight increase (65, 41, 54 and 41%, respectively) compared to shoot culture growth with the Murashige-Skoog nitrogen mix of 40 mM nitrate and 20 mM ammonium. Glutamate and proline were at best poorly supportive, and glycine betaine and choline were non-supportive. Callus initiation from leaf discs was supported only by nitrate, ammonium, urea, glutamine and proline (50, 100, 100, 100 and 80%, respectively, at the best concentrations, of that on Murashige-Skoog medium). Subsequent shoot regeneration from the intact disc callus in those cultures only occurred on media with nitrate, urea, glutamine, or proline (12, 3, 28 and 3% as many shoots, respectively, as on Murashige-Skoog medium). Overall, the Murashige-Skoog nitrogen mix was superior or equal to any single nitrogen source. However, single nitrogen source media with nitrate, ammonium, urea, glutamine or proline should have significant utility for shoot or leaf disc cultures of mutants with impaired nitrogen assimilation, in comparative physiology studies, or in dual cultures with pathogens of limited ability to use any of these forms of nitrogen.

Instrumentation for the remote monitoring of physiological and behavioral variables.

Few commercial products are available for investigators who wish to monitor multiple physiological and behavioral variables in unrestrained subjects. When telemetry is not practical, e.g., in studies of at-sea diving physiology, one of the only options is to design and build a custom data-logging instrument. This paper describes how a data logger was developed for the successful long-term monitoring of dive depth, swim speed, heart rate, water temperature, and multiple body temperatures from free-ranging northern elephant seals. The task was facilitated by using a commercially available single-board computer designed specifically for portable multichannel data acquisition and, where possible, off-the-shelf sensors/transducers available with integrated signal-conditioning circuits. A smaller data logger for monitoring the electrocardiogram, body temperature, and dive behavior of double-crested cormorants is also described to illustrate the flexibility and simplicity of this approach. Although it is customized for diving animals, with incorporation of the appropriate sensors the basic design should be applicable to studies of comparative, environmental, or exercise physiology involving most medium-to-large animals, including humans.

Description of Saccharomonospora xinjiangensis sp. nov. based on chemical and molecular classification

Comparative studies of morphology, physiology, biochemistry and chemical composition of cells, and phylogenetic analysis based on 16S rRNA gene sequences were carried out with strains XJ-54T and XJ-58 of the genus Saccharomonospora and type strains of related genera. The results indicated that the two strains are different from known members of the genus Saccharomonospora. A new species with the name Saccharomonospora xinjiangensis sp. nov. is proposed. The new species is characterized by the presence of longitudinal pairs of spores on both the aerial and the vegetative hyphae and contains phosphatidyl ethanolamine, phosphatidyl choline and unknown glucosamine-containing phospholipids, and the major menaquinones MK-9(H2), MK-9(H4) and MK-7(H4).

A comparative physiological and morphological study of Dendryphiella salina and D. arenaria in relation to adaptation to life in the sea

A series of comparative physiological and morphological analyses are described for eighteen Dendryphiella isolates. Conidial characteristics of ten isolates showed relatively little variation as a result of different incubation conditions. Isolates were markedly tolerant to NaCl and KCl, although some variation between isolates was noted. A variety of nitrogen compounds could be utilized by most isolates although some grew poorly with certain nitrogen sources. Most isolates showed a wide pH growth range, particularly at alkaline values, and broad temperature growth profiles. The relevance of these physiological characteristics to the survival and fitness of Dendryphiella species in the marine environment is discussed.

The signal in total-body plethysmography: errors due to adiabatic-isothermic difference

Total-body plethysmography is a technique often employed in comparative physiology studies because it avoids excessive handling of the animals. The pressure signal obtained is generated by an increase in internal energy of the gas phase of the system. Currently, this increase in internal energy is ascribed to heating (and water vapour saturation) of the inspired gas. The standard equation for computing tidal-volume implies that only temperature and saturation differences can be responsible for generating the ventilation signal. In this study, we were able to demonstrate that the difference between the external process of the thoracic expansion, which is adiabatic, and the internal process of it, which is isothermic, is an important factor of internal energy change in the total-body plethysmography method. In other words, organic tissues transfer heat to the entering gas but also to the present gas, in a way that keeps internal expansion an isothermic process. This extra amount of energy was never taken into account before. Therefore, experiments using such a technique to measure tidal-volume should be done using isothermic chambers. Moreover, due to uncertainties of the complementary measurements (ambient and lung temperatures, ambient water vapour saturation) needed to compute tidal-volume using total-body plethysmography, a minimal temperature difference about 15°C between body and ambient should exist to keep uncertainties in tidal-volume values below 5%. However, this limit is not absolute, because it varies as a function of humidity and degree of uncertainty of the complementary measurements.

Comparative investigation on the susceptibility of faba bean (Vicia faba L.) and sunflower (Helianthus annuus L.) to iron chlorosis

Comparative physiological studies on iron (Fe) chlorosis of Vicia faba L. and Helianthus annuus L. were carried out. High internal Fe contents in Vicia cotyledons (16–37 μg) were completely used for plant growth and Fe chlorosis was not inducible by the application of nitrate (with or without bicarbonate). In Helianthus, low quantities of Fe in the seeds (4 μg) were insufficient for normal growth and without Fe in the nutrient solution, Fe chlorosis was obtained in all treatments. This chlorosis was an absolute Fe deficiency. Also, the treatment with 1 μM Fe in the nutrient solution and nitrate (with or without bicarbonate) led to severe chlorotic symptoms associated with low leaf Fe concentrations and high Fe concentrations in the roots. In contrast, Helianthus grown with NH4NO3 and 1 μM Fe had green leaves and high leaf Fe concentrations. However, with NO3 supply (with or without bicarbonate), Fe translocation from the roots to the upper plant parts was restricted and leaves were chlorotic. Chlorotic and green sunflower leaves may have the same Fe concentrations, leaf Fe concentration being dependent on Fe translocation into the leaf at the various pH levels in the nutrient solution. At low external pH levels (controlled conditions) more Fe was translocated into the leaf leading to similar leaf Fe concentrations with higher chlorophyll concentrations (NH4NO3) and with lower chlorophyll concentrations (NO3). This indicates a lower utilization of leaf Fe of NO3 grown sunflower plants. Utilization of Fe in faba bean leaves is presumably higher than in sunflower leaves. In Vicia xylem sap pH was not affected by nitrate. In contrast, the xylem sap pH in Helianthus was permanently increased by about 0.4 pH units when fed with nitrate (with or without bicarbonate) compared with NH4NO3 nutrition. The xylem sap pH is indicative of leaf apoplast pH. From our earlier work (Mengel et al., 1994; Kosegarten und Englisch, 1994) we therefore suppose that in Helianthus, Fe immobilization occurs in the leaf apoplast due to high pH levels when grown with nitrate (with or without bicarbonate).

Grains or Veins: Is Enteral Nutrition Really Better Than Parenteral Nutrition? A Look at the Evidence

Enteral nutrition is said to be better than parenteral nutrition for providing nutrition support to humans. To assess the literature documenting the assertions that enteral nutrition is superior to parenteral nutrition with respect to cost, safety, physiology, intestinal structure and function, bacterial translocation, and outcome. Sources included MEDLINE search, personal files, and references from human comparative studies of enteral vs parenteral nutrition. The goal was to include all human studies directly addressing questions of comparative efficacy of enteral and parenteral nutrition. Emphasis was given to prospective randomized controlled studies where available. Retrospective comparisons were not included. An attempt was made to briefly summarize methodology and findings of relevant studies. No general attempt was made to assess quality of individual studies. Enteral nutrition appears to be less expensive than parenteral nutrition, but new economic analyses are needed given the newer aggressive access techniques for enteral nutrition. Enteral nutrition is associated with meaningful morbidity and mortality. The little comparative data existent suggest no differences in safety. Comparative studies of physiology and metabolism as well as comparative and noncomparative studies of intestinal function and structure do not support putative advantages of enteral nutrition. There is no evidence that enteral nutrition prevents bacterial translocation in humans. Enteral nutrition probably reduces septic morbidity compared with parenteral nutrition in abdominal trauma. Otherwise, there is no evidence that enteral nutrition consistently improves patient outcome compared with parenteral nutrition. With the exception of decreased cost and probable reduced septic morbidity in acute abdominal trauma, the available literature does not support the thesis that enteral nutrition is better than parenteral nutrition in humans.

PERSPECTIVES IN COMPARATIVE ECOPHYSIOLOGY OF SOME BRAZILIAN VEGETATION TYPES: LEAF CO2 ANDH2O GAS EXCHANGE, CHLOROPHYLL a FLUORESCENCE AND CARBON ISOTOPE DISCRIMINATION

Photosynthetic activity is responsible for the energy plants use for growth, defense and reproduction. Therefore, photosynthesis is fundamental to plant metabolism However, the effects of environmental factors on net CO 2 assimilation rates are as yet poorly known in Brazilian vegetation types. A decrease in net CO 2 uptake may be related to a decrease in CO, diffusion to the carboxylation sites due to partial or total stomata closure and to direct inhibition 01' primary and secondary photosynthetic processes in the chloroplasts. Photosynthetic carbon reduction is one of the rnost important pathways for the utilization of light energy. Hence, lower rates of CO, uptake may cause an excess of excitation energy through the photosystems and consequently le ad to a decline in the efficiency of photosynthetic energy conversion. The study of comparative ecophysiology of native species is essential for understanding the mechanisms that lead to the high diversity of the Brazilian flora. CO, and H 2 O gas exchange, chlorophyll a fluorescence and carbon isotope discrimination are powerful and predictive tools for addressing the influence of multi pie environmental factors on plant performance in situ. Here 1 discuss the results of comparative plant physiological ecology studies in several Brazilian vegetation types.

PERSPECTIVES IN COMPARATIVE ECOPHYSIOLOGY OF SOME BRAZILIAN VEGETATION TYPES: LEAF CO2 AND H2O GAS EXCHANGE, CHLOROPHYLL A FLUORESCENCE AND CARBON ISOTOPE DISCRIMINATION

Photosynthetic activity is responsible for the energy plants use for growth, defense and reproduction. Therefore, photosynthesis is fundamental to plant metabolism However, the effects of environmental factors on net CO 2 assimilation rates are as yet poorly known in Brazilian vegetation types. A decrease in net CO 2 uptake may be related to a decrease in CO, diffusion to the carboxylation sites due to partial or total stomata closure and to direct inhibition 01' primary and secondary photosynthetic processes in the chloroplasts. Photosynthetic carbon reduction is one of the rnost important pathways for the utilization of light energy. Hence, lower rates of CO, uptake may cause an excess of excitation energy through the photosystems and consequently le ad to a decline in the efficiency of photosynthetic energy conversion. The study of comparative ecophysiology of native species is essential for understanding the mechanisms that lead to the high diversity of the Brazilian flora. CO, and H 2 O gas exchange, chlorophyll a fluorescence and carbon isotope discrimination are powerful and predictive tools for addressing the influence of multi pie environmental factors on plant performance in situ. Here 1 discuss the results of comparative plant physiological ecology studies in several Brazilian vegetation types.

Comparative aspects on nitric oxide in brain and its role as a cerebral vasodilator

Histological studies have detected nitric oxide (NO) synthase in the central nervous system of all vertebrates examined, from lampreys to mamals. However, there are still very few comparative physiological studies on the function of NO synthase in the brain of non-mammalian vertebrates. So far, we know that acetylcholine can cause an NO-dependent increase in brain blood flow in turtles and some fish species (crucian carp and rainbow trout), whereas some other fishes appear to lack such a mechanism. Hypercapnia can induce NO-dependent cerebral vasodilation in mammals, but such a mechanism appears to be lacking in the ectothermic vertebrates examined. The number of species studied needs to be expanded before we can draw any firm conclusions about the origin of NO-dependent brain blood flow regulation: if it has evolved more than once or if it has been occasionally lost during evolution. We conclude that NO synthase may be present in all vertebrate brains but that its functions can vary, as judged from its role in cerebral blood flow regulation. The diversity of functions that NO has proven to have within the mammalian brain is likely to be paralleled by the same degree of diversity of function between vertebrate groups.

Identifying and Evaluating Patterns in Cardiorespiratory Physiology

SYNOPSIS. A major theme of many papers in this symposium is the identification of broad physiological trends and patterns that extend beyond the boundaries of data from individual studies. Recognizing patterns in everything from hypoxic ventilatory patterns to regulation of blood gases not only helps the investigator understand specific data sets, but also helps place those data in a broad context. Yet, recognizing physiological patterns is confounded by two factors: phylogenetic relationships and physiological state. Fortunately, the last decade has seen infiltration of sound evolutionary theory, including tools of cladisitic analysis and population genetics, into more and more studies of comparative physiology. However, even when an experimenter carefully accounts for phytogeny, differences in physiological state in the experimental animals can still obscure physiological patterns. Two informal categories of physiological state are described, the first obvious and frequently controlled for, and the second less obvious and typically not controlled for. Examples of the latter, including seasons, rhythms, prandial effects and sex of the animal, are developed to show how ignoring these can lead to considerable misleading variation in cardiorespiratory data sets. Considering physiological state is vital in producing reliable data that can be used meaningfully for delineating broad physiological patterns.

Molecular mechanisms for the regulation of water transport in amphibian epithelia by antidiuretic hormone

Classic laboratory studies performed in the 1950's and 1960's focused on the structures and biochemical actions of multiple neurohypophysial peptides that possessed profound effects on the overall water balance of many vertebrates [reviewed in 1]. These data emphasized the importance of antidiuretic hormones (ADH) in the evolution of vertebrates and provided a framework for our current understanding of their roles in renal function. In a similar fashion, the recent discovery of the family of aquaporin water channel proteins has supplied new tools to examine the molecular aspects of ADH-elicited water transport in epithelial physiology. Data concerning the structure and distribution of aquaporin water channels have been further advanced by recent research defining several of the most basic aspects of hormonally regulated transport in many cell types. Together, these findings have provided many new insights into the apical membrane events set in motion by the binding of ADH to the basolateral membrane of epithelial cells. The purpose of this review is to highlight the role of the ADH-elicited water permeability response in the terrestrial adaptation of amphibians and their evolutionary offspring, mammals including humans. To accomplish this, we have divided the review into three sections. The first section summarizes published data from studies in comparative physiology involving the evolution and distribution of the ADH-elicited water permeability response in various amphibian species. The second section provides an overview of the vesicle mediated water permeability response in toad bladder and mammals. In this selective review, we have emphasized several common features present in ADH-mediated insertion and removal of water channel containing vesicles and the insulin-induced vesicular translocation of a facilitative glucose transport protein. The third section re-examines two important questions about the evolution of the ADH-elicited water permeability response in light of recent data reviewed in the prior section. Taken together, these data illustrate that future research in this area will provide new insights into the origins of the ADH-elicited water permeability response through use of probes specific for various aquaporin water channel proteins.

A comparative physiological and morphological study of periodontal ligament mechanoreceptors represented in the trigeminal ganglion and the mesencephalic nucleus of the cat

A correlative morphological study was carried out on two electrophysiologically identified and located periodontal ligament mechanoreceptors in anaesthetised cats. One mechanoreceptor had its cell body in the mesencephalic nucleus and the other had its cell body in the trigeminal ganglion. Physiological recordings were made from each of their cell bodies. The two receptors were located by punctate and electrical stimuli in the labial aspect of the periodontal ligament of the left mandibular canine tooth. Both receptors had similar positions relative to the tooth apex and fulcrum and were situated in the labial part of the ligament in each tooth. The receptor loci were marked, and these regions were studied in a series of semi-thin and ultra-thin sections. Only Ruffini nerve endings were observed under each ink mark. Both Ruffini nerve endings branched, were unencapsulated and were incompletely surrounded by terminal Schwann cells with extensions projecting towards collagen bundles. The results indicate that periodontal ligament mechanoreceptors with cell bodies in the mesencephalic nucleus and those with their cell bodies in the trigeminal ganglion can both be Ruffini nerve endings. Furthermore, there was no apparent morphological difference between the two periodontal ligament mechanoreceptors.