Anatomy, biology, physiology and basic pathology of the nail organ

The nail is the largest skin appendage. It grows continuously through life in a non-cyclical manner; its growth is not hormone-dependent. The nail of the middle finger of the dominant hand grows fastest with approximately 0.1 mm/day, whereas the big toe nail grows only 0.03-0.05 mm/d. The nails' size and shape vary characteristically from finger to finger and from toe to toe, for which the size and shape of the bone of the terminal phalanx is responsible. The nail apparatus consists of both epithelial and connective tissue components. The matrix epithelium is responsible for the production of the nail plate whereas the nail bed epithelium mediates firm attachment. The hyponychium is a specialized structure sealing the subungual space and allowing the nail plate to physiologically detach from the nail bed. The proximal nail fold covers most of the matrix. Its free end forms the cuticle which seals the nail pocket or cul-de-sac. The dermis of the matrix and nail bed is specialized with a morphogenetic potency. The proximal and lateral nail folds form a frame on three sides giving the nail stability and allowing it to grow out. The nail protects the distal phalanx, is an extremely versatile tool for defense and dexterity and increases the sensitivity of the tip of the finger. Nail apparatus, finger tip, tendons and ligaments of the distal interphalangeal joint form a functional unit and cannot be seen independently. The nail organ has only a certain number of reaction patterns that differ in many respects from hairy and palmoplantar skin.

Long-term hyperexcitability of sensory and motor axons in Aplysia californica: Induction by axotomy, serotonin, and transient depolarization

Neuropathic pain is a debilitating neurological disorder that may appear after peripheral nerve trauma and is characterized by persistent, intractable pain. The well-studied phenomenon of long-term hyperexcitability (LTH), in which sensory somata become hyperexcitable following peripheral nerve injury may be important for both chronic pain and long-lasting memory formation, since similar cellular alterations take place after both injury and learning. Though axons have previously been considered simple conducting cables, spontaneous afferent signals develop from some neuromas that form at severed nerve tips, indicating intrinsic changes in sensory axonal excitability may contribute to this intractable pain. Here we show that nerve transection, exposure to serotonin, and transient depolarization induce long-lasting sensory axonal hyperexcitability that is localized to the treated nerve segment and requires local translation of new proteins. Long-lasting functional plasticity may be a general property of axons, since both injured and transiently depolarized motor axons display LTH as well. Axonal hyperexcitability may represent an adaptive mechanism to overcome conduction failure after peripheral injury, but also displays key features shared with cellular analogues of memory including: site-specific changes in neuronal function, dependence on transient, focal depolarization for induction, and requirement for synthesis of new proteins for expression of long-lasting effects. The finding of axonal hyperexcitability after nerve injury sheds new light on the clinical problem of chronic neuropathic pain, and provides more support for the hypothesis that mechanisms of long-term memory storage evolved from primitive adaptive responses to injury. ^

Depolarization-dependent synaptic potentiation and hyperexcitability induced by a Ca2+-independent trigger

Despite vast research efforts since Cajal's seminal thoughts on the adaptation of the nervous system, researchers have only recently begun to understand the diversity of forms of neuronal plasticity and its mechanisms. All known forms of activity-dependent neuronal plasticity utilize alterations in [Ca 2+]i as a signal of changes in the membrane voltage. Ca 2+ sensors trigger modifications in excitability or synaptic strength that last from seconds to weeks and presumably years. Intriguingly, Kunjilwar et al., (unpublished observations) discovered in peripheral sensory axons of Aplysia that the induction of depolarization-dependent long-term axonal hyperexcitability does not require Ca2+ transients. Here we show that induction of depolarization-dependent intermediate-term and long-term synaptic potentiation in Aplysia occurs in conditions that prevent Ca2+ entry through voltage-gated channels and elevation of [Ca2+]i. We found that the intermediate-term synaptic potentiation induced under conditions expected to prevent Ca 2+ transients is associated with increased excitability of sensory neuron axons near presynaptic terminals, suggesting that the synaptic potentiation involves a presynaptic locus. The Ca2+-independent intermediate- and long-term synaptic potentiation appeared similar to previously reported Ca2+-dependent modifications in Aplysia. ^

Physiological Effects of Alcohol on Crayfish Escape Circuitry

Alcohol is one of the oldest and most widely used drugs on the planet, but the cellular mechanisms by which it affects neural function are still poorly understood. Unlike other drugs of abuse, alcohol has no specific receptor in the nervous system, but is believed to operate through GABAergic and serotonergic neurotransmitter systems. Invertebrate models offer circuits of reduced numerical complexity and involve the same cell types and neurotransmitter systems as vertebrate circuits. The well-understood neural circuits controlling crayfish escape behavior offer neurons that are modulated by GABAergic inhibition, thus making tail-flip circuitry an effective circuit model to study the cellular mechanisms of acute alcohol exposure. Crayfish are capable of two stereotyped, reflexive escape behaviors known as tail-flips that are controlled by two different pairs of giant interneurons, the lateral giants (LG) and the medial giants (MG). The LG circuit has been an established model in the neuroscience field for more than 60 years and is almost completely mapped out. In contrast, the MG is still poorly understood, but has important behavioral implications in social behavior and value-based decision making. In this dissertation, I show that both crayfish tail-flip circuitry are physiologically sensitive to relevant alcohol concentrations and that this sensitivity is observable on the single cell level. I also show that this ethyl alcohol (EtOH) sensitivity in the LG can be changed by altering the crayfish’s recent social experience and by removing descending inputs to the LG. While the MG exhibits similar physiological sensitivity, its inhibitory properties have never been studied before this research. Through the use of electrophysiological and pharmacological techniques, I show that the MG exhibits many similar inhibitory properties as the LG that appear to be the result of GABA-mediated chloride currents. Finally, I present evidence that the EtOH-induced changes in the MG are blocked through pre-treatment of the potent GABAA receptor agonist, muscimol, which underlines the role of GABA in EtOH’s effects on crayfish tail-flip circuitry. The work presented here opens the way for crayfish tail-flip circuitry to be used as an effective model for EtOH’s acute effects on aggression and value-based decision making.

Annotated bibliography II of the hard clam Mercenaria mercenaria

In this era of proliferating scientific information it is difficult to keep up with the literature, even in one's own field. Review articles are helpful in summarizing the status of knowledge. In oyster biology, several such published reviews have been of great help to working scientists. The outstanding contributions that come to' mind are those by Baughman (1948), Korringa (1952), Joyce (1972), Breisch and Kennedy (1980), and Kennedy and Breisch (198 I). If done well, such compilations serve as checkpoints, eliminating or vastly reducing the need to consult the literature in detail. On Long Island, New York, where the hard clam Mercenaria mercenaria is the major commercial resource, we have felt the need for some time for a compendium of knowledge on this important mollusk. Several years ago my secretary, students, and I began to gather materials for an annotated bibliography. We have already published a collection of 2233 titles (McHugh et al. 1982), nearly all accompanied by abstracts, and in this publication we have added another 460. The experience has been rewarding. We have been surprised at the extent of the literature, much of it only remotely related to the shellfish industry itself, but nevertheless throwing light on the biology, physiology, and many other aspects of the scientific knowledge of hard clams. The following bibliography is divided into three parts. Part I comprises the bulk of the bibliography, while Parts 2 and 3 contain additional titles that we decided to include during editing, submission, and approval of the manuscript for publication. All three parts are indexed together, however. We also reexamined those titles in the previous bibliography (McHugh et al. 1982) which did not include abstracts. These are included in Parts 2 and 3 of this bibliography. Most of these contained no specific reference to Mercenaria mercenaria. A few searches were terminated for various reasons. (PDF file contains 66 pages.)

Cryopreservation of rhesus macaque (Macaca mulatta) spermatozoa and their functional assessment by in vitro fertilization

Although spermatozoa from several species of nonhuman primates have been cryopreserved, there has been no report of success with rhesus macaque spermatozoa as judged by functional assays. Two Tris-egg yolk freezing media. TEST and TTE. which have: been successfully used for cynomolgus macaque (Macaca fascicularis) spermatozoa, were compared for cryopreservation of spermatozoa From four rhesus macaques (Macaca mulatta). The postthaw motility (percentage and duration) of spermatozoa cryopreserved in TTE was much higher than that for spermatozoa cryopreserved in TEST. The function of sperm cryopreserved in TTE was evaluated by in vitro fertilization or oocytes collected from gonadotropin-stimulated prepubertal rhesus macaques. Of the inseminated oocytes. 82 +/- 13% were fertilized and 63 +/- 22 and 39 +/- 21% of the resulting zygotes developed into morulae and blastocysts. respectively. These results indicate that rhesus macaque spermatozoa can be effectively cryopreserved in TTE medium. This finding will facilitate the application of in vivo and in vitro assisted reproductive technologies in this species. (C) 2001 Academic Press.

Molecular and expression characterization of two somatostatin genes in the Chinese sturgeon, Acipenser sinensis

Chinese sturgeon (Acipenser sinensis) is a rare and endangered species and also an important resource for the sturgeon aquaculture industry. SMART cDNA was synthesized from the hypothalamus of Chinese sturgeon, and the full-length cDNAs of two somatostatin (SS) genes were cloned and sequenced. The first cDNA (AsSS1) encodes a 116-amino acid protein that contains the SS14 sequence at its C-terminal extremity. AsSS1 shows high identity to that of human and other vertebrates. The second cDNA (AsSS2) encodes a 111-amino acid protein that contains the somatostatin variant [Pro(2)]-SS14 at its C-terminal extremity. Both the two SS mRNAs were expressed in brain and pituitary with different mRNA levels. But in peripheral tissues, AsSS2 was more widely distributed than AsSS1. High mRNA levels of AsSS2 were found in liver, kidney and heart, while low mRNA levels of AsSS2 were also detected in ovary. Throughout embryogenesis and early larval development only AsSS2 mRNAs were detected. Furthermore, in the hypothalamus of one to five year-old Chinese sturgeon, AsSS2 but not AsSS1 maintained stable expression. The mRNA distribution suggests that the Chinese sturgeon AsSS2 products play important physiological functions in adult fish as well as in cell growth and organ differentiation in embryo and larva development. (C) 2009 Elsevier Inc. All rights reserved.

Nutritional homeostasis in carnivorous southern catfish (Silurus meridionalis): is there a mechanism for increased energy expenditure during carbohydrate overfeeding?

In previous growth experiments with carnivorous southern catfish (Silurus meridionalis), the non-fecal energy lose was positively related to dietary. carbohydrate level. To test whether metabolic energy expenditure accounts for such energy loss, an experiment was performed with southern catfish juveniles (33.2-71.9 g) to study the effect of dietary carbohydrate level on fasting metabolic rate and specific dynamic action (SDA) at 27.5 degreesC. The fasting metabolic rate in this catfish was increased with dietary carbohydrate level, and the specific dynamic action (SDA) coefficient (energy expended on SDA as percent of assimilated energy) was not affected by dietary carbohydrate level. The results suggest that in southern catfish, carbohydrate overfeeding increases metabolic rate to oxidize unwanted assimilated carbohydrate. A discussion on the poor capacity of intermediate metabolism for adapting dietary carbohydrate in carnivorous fish and its possible relationship with facultative component of SDA was also documented in this paper. (C) 2004 Elsevier Inc. All rights reserved.

Resting metabolism and heat increment of feeding in mandarin fish (Siniperca chuatsi) and Chinese snakehead (Channa argus)

Resting metabolism was measured in immature mandarin fish Siniperca chuatsi weighing 42.1-510.2 g and Chinese snakehead Channa argus weighing 41.5-510.3 g at 10, 15, 20, 25, 30 and 35 degreesC. Heat increment of feeding was measured in mandarin fish weighing 202.0 (+/-14.0) g and snakehead weighing 200.8 (+/-19.3) g fed swamp leach Misgurnus anguillicaudatus at 1% body weight per day at 28 degreesC. In both species, weight exponent in the power relationship between resting metabolism and body weight was not affected by temperature. The relationship between resting metabolism and temperature could be described by a power function. The temperature exponent was 1.39 in mandarin fish and 2.10 in snakehead (P < 0.05), indicating that resting metabolism in snakehead increased with temperature at a faster rate than in mandarin fish. Multiple regression models were used to describe the effects of body weight (W, g) and temperature (T, C) on the resting metabolism (R-s, mg O-2/h): In R-s = - 5.343 + 0.772 In W + 1.387 In T for the mandarin fish and In R-s = -7.863 + 0.801 ln W + 2.104 In T for the Chinese snakehead. The proportion of food energy channelled to heat increment was 8.7% in mandarin fish and 6.8% in snakehead. (C) 2000 Elsevier Science Inc. All rights reserved.