Neurochemistry of the dorsal horn

The dorsal horn region of the spinal cord, particularly the dorsal root entry zone (DREZ), represents the first central integration center for nociceptive afferent impulses. Here, the excitatory neurotransmitters/modulators, products of the primary sensory neurons, are released, the segmental interneuronal influences pertain, and the descending bulbospinal tracts terminate. A vast variety of compounds are thus involved in the processing of nociceptive information in these areas, among which are the 'classical' neurotransmitters and the more recently described neuropeptides. A continued vast interest exists concerning the chemistry of the dorsal horn/DREZ region. The current developments and understanding regarding the pharmacology of this region are presented. Particular emphasis is given to the interactions among the various compounds, the coexistence of some of these within single neuronal populations, the importance of the opiate receptor subtypes, and the actions and localizations of some of the newly discovered neuropeptides.     

Prolapse of the nongravid horn in a cow with a seven-month pregnancy: A case report

Prolapse of the right nongravid horn of the uterus in a cow with a 7 1 2 - mo pregnancy is reported. The condition occurred 4 d after a vagino-cervical prolapse was reduced and fixed by Minchev's technique. The everted uterine horn together with its corresponding ovary became gangrenous and detached due to eschemic necrosis resulting from the constriction of the partially closed cervix. The cow delivered a healthy bull calf without any complications 6 wk after the incidence. Rectal examination of the cow 3 mo later showed completion of involution, uterus unicornis with its left ovary and a mature corpus luteum. The absence of the right ovary and the right uterine horn did not seem to interfere with the normal estrous cycle.     

Variation in the ontogenetic allometry of horn length in bovids along a body mass continuum

Allometric relationships describe the proportional covariation between morphological, physiological, or life‐history traits and the size of the organisms. Evolutionary allometries estimated among species are expected to result from species differences in ontogenetic allometry, but it remains uncertain whether ontogenetic allometric parameters and particularly the ontogenetic slope can evolve. In bovids, the nonlinear evolutionary allometry between horn length and body mass in males suggests systematic changes in ontogenetic allometry with increasing species body mass. To test this hypothesis, we estimated ontogenetic allometry between horn length and body mass in males and females of 19 bovid species ranging from ca. 5 to 700 kg. Ontogenetic allometry changed systematically with species body mass from steep ontogenetic allometries over a short period of horn growth in small species to shallow allometry with the growth period of horns matching the period of body mass increase in the largest species. Intermediate species displayed steep allometry over long period of horn growth. Females tended to display shallower ontogenetic allometry with longer horn growth compared to males, but these differences were weak and highly variable. These findings show that ontogenetic allometric slope evolved across species possibly as a response to size‐related changes in the selection pressures acting on horn length and body mass.     

Giant cutaneous horn in an African woman: a case report

Introduction

A cutaneous horn is a conical projection of hyperkeratotic epidermis. Though grossly resembling an animal horn, it lacks a bony core. These lesions have been well described in Caucasian patients, as well as in a number of Arabic and Asian patients.

Case presentation

A young female presented with a large 'horn' of five-year duration, arising from a burn scar. Excision and scalp reconstruction were performed. Histology was reported as verrucoid epidermal hyperplasia with cutaneous horn.

Conclusion

This may be the first documentation of this lesion in a black African. Although likely rare, it should be considered in the differential diagnosis of dermatologic lesions. Up to 40% of cutaneous horns occur as part of a premalignant or malignant lesion, and surgical extirpation with histological examination is thus more important than the curiosity surrounding these lesions.

     

去甲肾上腺素在脊髓背角的镇痛机制

疹髓背角浅层是传递和调制外周伤害性信息的关键部位。起源于脑干的去甲肾上腺素（NA）能纤维终止脊髓背角,它们释放的NA具有抑制初级传入末梢释放谷氨酸和P物质、增加Ⅱ层（胶状质）抑制性神经活性物质释放的作用。此外,形态学研究提示NA可能直接抑制Ⅰ/Ⅲ层向丘脑传递伤害性信息的投射神经元。NA可能通过以上途径,实现对外周伤害性信息传递的调制而发挥镇痛作用。     

Neuronal circuitry for pain processing in the dorsal horn

Neurons in the spinal dorsal horn process sensory information, which is then transmitted to several brain regions, including those responsible for pain perception. The dorsal horn provides numerous potential targets for the development of novel analgesics and is thought to undergo changes that contribute to the exaggerated pain felt after nerve injury and inflammation. Despite its obvious importance, we still know little about the neuronal circuits that process sensory information, mainly because of the heterogeneity of the various neuronal components that make up these circuits. Recent studies have begun to shed light on the neuronal organization and circuitry of this complex region.     

Power law dispersion in animal horn

The dielectric response of sheep horn has been measured in the frequency range from 10^–3–10⁵ Hz and over temperatures in the range 304–500 K. The dynamic behaviour of the conductance and capacitance in sheep horn has been observed to follow fractional power law dependences on frequency. It is shown that the over all dielectric response of these dead cells correspond to a dispersive imperfect bulk in series with a dispersive barrier region. It is further shown that the increase in temperature influences the reponse by eliminating the room temperature dc conductance and affecting the magnitude of the dispersion in capacitance. The magnitudes of activation energies are found as 0.33±0.02 eV for conductance, 0.40±0.02 eV for relaxation and 0.33±0.02 eV for the frequency shift.     

Assembly of the dorsal horn somatotopic map

We hypothesize: (a) peripheral innervation densities determine map scales in dorsal horn, (b) dorsal horn cell (DHC) receptive field (RF) geometries are determined by map scales, and (c) morphologies of primary afferents (PAs) and DHCs reflect their developmental history. We suggest the following sequence: (A) PAs project in a somatotopic mediolateral sequence. (B) DHCs assemble prototype RFs by sampling presynaptic neuropil with their dendrites. (C) PAs then project to all levels where their RFs are contained within prototype RFs of DHCs. (D) A competitive mechanism produces the adult form of DHC RFs. (E) Adult distributions of PA terminals and DHC dendrites reflect this developmental history. (F) Mediolateral somatotopic gradients are determined by RF densities of axons entering at the same levels. (G) Map scales at different rostrocaudal levels are determined by somatotopic gradients. (H) Geometries of DHC RFs are determined by constant convergence and divergence of monosynaptic connections. (I) Secondary processes further modify geometries of DHC RFs. (J) Residual self-organizing capacity supports maintenance and plastic mechanisms. We adduce the following evidence: (1) agreement between monosynaptically coupled inputs and cells' excitatory low threshold mechanoreceptive fields; (2) the temporal sequence of events during penetration of the gray matter by PAs; (3) variation of PA terminal and DHC dendritic domains as a function of map scale; (4) somatotopic gradients and geometries of DHC RFs in adult dorsal horn; (5) calculations of peripheral innervation densities and dorsal horn map scales; and (6) constant divergence and convergence between PAs and DHCs.     

Heterogeneity in male horn growth and longevity in a highly sexually dimorphic ungulate

In sexually dimorphic ungulates, sexual selection favoring rapid horn growth in males may be counterbalanced by a decrease in longevity if horns are costly to produce and maintain. Alternatively, if early horn growth varied with individual quality, it may be positively correlated with longevity. We studied Alpine ibex Capra ibex in the Gran Paradiso National Park, Italy, to test these alternatives by comparing early horn growth and longevity of 383 males that died from natural causes. After accounting for age at death, total horn length after age 5 was positively correlated with horn growth from two to four years. Individuals with the fastest horn growth as young adults also had the longest horns later in life. Annual horn growth increments between two and six years of age were independent of longevity for ibex whose age at death ranged from 8 to 16 years. Our results suggest that growing long horns does not constrain longevity. Of the variability in horn length, 22% could be explained by individual heterogeneity, suggesting persistent differences in phenotypic quality among males. Research on unhunted populations of sexually dimorphic ungulates documents how natural mortality varies according to horn or antler size, and can help reduce the impact of sport hunting on natural processes.     

Evolutionary allometry reveals a shift in selection pressure on male horn size

How selection pressures acting within species interact with developmental constraints to shape macro‐evolutionary patterns of species divergence is still poorly understood. In particular, whether or not sexual selection affects evolutionary allometry, the increase in trait size with body size across species, of secondary sexual characters, remains largely unknown. In this context, bovid horn size is an especially relevant trait to study because horns are present in both sexes, but the intensity of sexual selection acting on them is expected to vary both among species and between sexes. Using a unique data set of sex‐specific horn size and body mass including 91 species of bovids, we compared the evolutionary allometry between horn size and body mass between sexes while accounting for both the intensity of sexual selection and phylogenetic relationship among species. We found a nonlinear evolutionary allometry where the allometric slope decreased with increasing species body mass. This pattern, much more pronounced in males than in females, suggests either that horn size is limited by some constraints in the largest bovids or is no longer the direct target of sexual selection in very large species.     

Inhibitory effects of dorsal horn and excitant effects of ventral horn intraspinal microinjections of norepinephrine and serotonin in the cat

Norepinephrine and serotonin microinjections (10 μg) into the dorsal spinal gray matter depressed C-fiber reflexes induced by electrical stimulation of the superficial peroneal nerve or radiant heat stimulation of the footpad. Microinjection of norepinephrine or serotonin into the ventral gray matter facilitated C-fiber reflexes. These studies lend support to the suggestion that dorsal horn projections of neuronal systems which utilized norepinephrine or serotonin as neurotransmitters inhibit nociceptive spinal reflexes, and ventral horn projections facilitate spinal reflexes.