• Title/Summary/Keyword: pseudorabies

Search Result 46, Processing Time 0.027 seconds

Neural pathway innervating ductus Deferens of rats by pseudorabies virus and WGA-HRP (흰쥐에서 WGA-HRP와 pseudorabies virus를 이용한 정관의 신경로에 대한 연구)

  • Lee, Chang-Hyun;Chung, Ok-Bong;Ko, Byung-Moon;Lee, Bong-Hee;Kim, Soo-Myung;Kim, In-Shik;Yang, Hong-Hyun
    • Korean Journal of Veterinary Research
    • /
    • v.43 no.1
    • /
    • pp.11-24
    • /
    • 2003
  • This experimental studies was to investigate the location of PNS and CNS labeled neurons following injection of 2% WGA-HRP and pseudorabies virus (PRY), Bartha strain, into the ductus deferens of rats. After survival times 4-5 days following injection of 2% WGA-HRP and PRV, the rats were perfused, and their brain, spinal cord, sympathetic ganglia and spinal ganglia were frozen sectioned ($30{\mu}m$). These sections were stained by HRP histochemical and PRY inummohistochemical staining methods, and observed with light microscope. The results were as follows ; 1. The location of sympathetic ganglia projecting to the ductus deferens were observed in pelvic ganglion, inferior mesenteric ganglion and L1-6 lwnbar sympathetic ganglia. 2. The location of spinal ganglia projecting to the ductus deferens were observed in T13-L6 spinal ganglia. 3. The PRY labeled neurons projecting to the ductus deferens were observed in lateral spinal nucleus, lamina I, II and X of cervical segments. In thoracic segments, PRY labeled neurons were observed in dorsomedial part of lamina I, II and III, and dorsolateral part of lamina IV and V. Densely labeled neurons were observed in intermediolateral nucleus. In first lumbar segment, labeled neurons were observed in intermediolateral nucleus and dorsal commisural nucleus. In sixth lumbar segment and sacral segments, dense labeled neurons were observed in sacral parasympathetic nuc., lamina IX and X. 4. In the medulla oblongata, PRV labeled neurons projecting to the ductus deferens were observed in the trigeminal spinal nuc., A1 noradrenalin cells/C1 adrenalin cells/caudoventrolateral reticular nuc., rostroventrolateral reticular nuc., area postrema, nuc. tractus solitarius, raphe obscurus nuc., raphe pallidus nuc., raphe magnus nuc., parapyramidal nuc., lateral reticular nuc., gigantocellular reticular nuc.. 5. In the pons, PRV labeled neurons projecting to the ductus deferens were ohserved in parabrachial nuc., Kolliker-Fuse nuc., locus cooruleus, subcooruleus nuc. and AS noradrenalin cells. 6. In midbrain, PRV labeled neurons projecting to the ductus deferens were observed in periaqueductal gray substance, substantia nigra and dorsal raphe nuc.. 7. In the diencephalon, PRV labeled neurons projecting to the ductus deferens were observed in paraventricular hypahalamic nuc., lateral hypothalamic nuc., retrochiasmatic nuc. and ventromedial hypothalamic nuc.. 8. In cerebrum, PRV labeled neurons projecting to the ductus deferens were observed in area 1 of parietal cortex. These results suggest that WGA-HRP labeled neurons of the spinal cord projecting to the rat ductus deferens might be the first-order neurons related to the viscero-somatic sensory and sympathetic postganglionic neurons, and PRV labeled neurons of the brain and spinal cord may be the second and third-order neurons response to the movement of smooth muscles in ductus deferens. These PRV labeled neurons may be central autonomic center related to the integration and modulation of reflex control linked to the sensory and motor system monitaing the internal environment. These observations provide evidence for previously unknown projections from ductus deferens to spinal cord and brain which may be play an important neuroanatornical basic evidence in the regulation of ductus deferens function.

Morphological Studies of the Central Neural Pathways to the Pancreas, Sanyinjiao(Sp6) and Yinlingquan(Sp9) using Pseudorabies Virus (Pseudorabies virus를 이용한 췌장과 삼음교(三陰交)(Sp6), 음릉천(陰陵泉)(Sp9)에서 투사되는 중추 신경로에 관한 형태학적 연구)

  • Kim, Cheol-Han;Lee, Su-Kyung;Yeom, Seung-Ryong;Kwon, Young-Dal;Song, Yung-Sun
    • Journal of Korean Medicine Rehabilitation
    • /
    • v.19 no.1
    • /
    • pp.23-38
    • /
    • 2009
  • Objectives : The purpose of this morphological studies was to investigate the relations between Sanyinjiao(Sp6), Yinlingquan(Sp9) and pancreas of rats using peudorabies virus(PRV). Methods : We observed labeled neurons following the injection of PRV, Bartha strain, into the Sanyinjiao(Sp6), Yinlingquan(Sp9) and pancreas of rats. After survival times of 4 days following the injection of PRV, the rats were perfused, and their spinal ganglia, spinal cord and brain stem were frozen sectioned($35{\mu}m$). These sections were strained by PRV immunohistchemical staining methods and observed with light microscope. Results : The results were as follows. 1. In the spinal ganglia, the overlap areas of PRV labeled neurons projecting to Sanyinjiao(Sp6), Yinlingquan(Sp9) and pancreas were observed in T10-13 dorsal root ganglia. 2. In the spinal cord, the overlap areas of PRV labeled neurons projecting to Sanyinjiao(Sp6), Yinlingquan(Sp9) and pancreas were lamina I, IV, V, VII, IX, X, intermediolateral nucleus(IML), intermediomedial nucleus(IMM) in thoracic segments. In lumbar segments, the overlap areas of PRV labeled neuron were lamina I, IV, V, VI, IX, X and IMM. In sacral segments, the overlap areas of PRV labeled neuron were lamina I, IV, V, VI, VII, IX, X. 3. In the brain, the overlap areas of PRV labeled neurons projecting to Sanyinjiao(Sp6), Yinlingquan(Sp9) and pancreas were area postrema, nucleus tractus solitarius, caudoventrolateral reticular nu., medullary reticular nu., lateral paragigantocellular nu., C3 adrenalin cells, gigantocellular nu., raphe pallidus nu., raphe obscurus nu., ambiguus nu., raphe magnus nu., pontine reticular formation, A5 cell group, subcoeruleus nu., locus coeruleus, Barringnton's nu., $K{\ddot{o}}lliker$-Fuse nu., dorsal raphe nu., Edinger-Westphal nu., central gray matter, perifornical nu., dorsomedial hypothalamic nu., arcuate nu., lateral hypothalamic nu., paraventricular hypothalamic nu., hindlimb area. Conclusions : In conclusion, these results suggest that the interrelationship of meridian(spleen meridian), acupoints(Sp6 and Sp9) and viscera(pancreas) may be related the central autonomic centers.

Therapeutic Strategy for the Prevention of Pseudorabies Virus Infection in C57BL/6 Mice by 3D8 scFv with Intrinsic Nuclease Activity

  • Lee, Gunsup;Cho, SeungChan;Hoang, Phuong Mai;Kim, Dongjun;Lee, Yongjun;Kil, Eui-Joon;Byun, Sung-June;Lee, Taek-Kyun;Kim, Dae-Hyun;Kim, Sunghan;Lee, Sukchan
    • Molecules and Cells
    • /
    • v.38 no.9
    • /
    • pp.773-780
    • /
    • 2015
  • 3D8 single chain variable fragment (scFv) is a recombinant monoclonal antibody with nuclease activity that was originally isolated from autoimmune-prone MRL mice. In a previous study, we analyzed the nuclease activity of 3D8 scFv and determined that a HeLa cell line expressing 3D8 scFv conferred resistance to herpes simplex virus type 1 (HSV-1) and pseudorabies virus (PRV). In this study, we demonstrate that 3D8 scFv could be delivered to target tissues and cells where it exerted a therapeutic effect against PRV. PRV was inoculated via intramuscular injection, and 3D8 scFv was injected intraperitoneally. The observed therapeutic effect of 3D8 scFv against PRV was also supported by results from quantitative reverse transcription polymerase chain reaction, southern hybridization, and immunohistochemical assays. Intraperitoneal injection of 5 and $10{\mu}g$ 3D8 scFv resulted in no detectable toxicity. The survival rate in C57BL/6 mice was 9% after intramuscular injection of 10 $LD_{50}$ PRV. In contrast, the 3D8 scFv-injected C57BL/6 mice showed survival rates of 57% ($5{\mu}g$) and 47% ($10{\mu}g$). The results indicate that 3D8 scFv could be utilized as an effective antiviral agent in several animal models.

The Oxytocinergic Neurons in Hypothamo-hypophysial Tract Contributes to CNS Pathway Innervating Ovary in Rat (시상하부-뇌하수체로 Oxytocin신경세포의 난소로 투사하는 중추신경로에 관한 연구)

  • Byun, Kyung-Hee;Oh, Jee-Hyun;Jo, Seung-Mook;Lee, Bong-Hee
    • Applied Microscopy
    • /
    • v.40 no.4
    • /
    • pp.211-218
    • /
    • 2010
  • The mammalian ovary is innervated by sympathetic and sensory neurons which contribute to regulating several aspects of ovarian function, including blood flow, steroidogenesis and follicular development. The existence of a neural connection between central neurons and the ovary has been rarely reported, but the mechanism underlying integration of ovarian activity to broader neuroendocrine responses has not been reported. We have now used a viral transneuronal tracing technique combined with a conventional retrograde labeling procedure of CT-HRP to demonstrate that oxytocin-producing neurons of the hypothalamus are synaptically connected to the ovary. Since ovarian activity is suppressed but the activity of oxytocin neurons is increased during breast feeding. Our finding that the oxytocinergic neural connection is likely to provide a direct transsynaptic mechanism by which the central nervous system maintains the state of infertility that accompanies lactation in mammals.

Central Neural Pathways Projecting to the Acupoints B62 and K6 Using the Neural Tracer (신경추적자를 이용한 신맥과 조해에서 투사되는 신경원의 표지부위에 대한 연구)

  • Kim, Su-Hyun;Lee, Chang-Hyun;Yuk, Sang-Won;Lee, Kwang-Gyu;Lee, Tae-Young;Lee, Sang-Ryoung
    • Journal of Acupuncture Research
    • /
    • v.18 no.2
    • /
    • pp.51-66
    • /
    • 2001
  • The purpose of this morphological studies was to investigate the central neural pathway projecting to the acupoints $B_{62}$ and $K_6$ using the neuroanatomical method following injection of transsynaptic neurotropic virus, pseudorabies virus(PRV-Ba and PRV-Ga) into the $B_{62}$ and $K_6$. After survival times of 96 hours following injection into the twenty rats with PRV-Ba(Bartha strain) and PRV-Ga(Bartha strain, ${\beta}$-galacidodase insertion). They were perfused, and their spinal cord and brain were frozen sectioned($30{\mu}m$). These sections were stained by X-gal histochemical and PRV immunohistochemical staining method, and observed with light microscope. The results were as follows : 1. In spinal cord, overlaped PRV-Ba and PRV-Ga labeled neurons projecting to the $B_{62}$ and $K_6$ were founded in thoracic, lumbar and sacral spinal segments. In thoracic spinal segments, Densely labeled areas were founded in lamina IV, V, VII(intermediolateral nucleus) and X areas. In lumbar segemnts, labeled areas were founded in lamina II, IV, V and X areas. In sacral spinal segments, labeled areas were founded in lamina IV, V and VI areas. 2. In brain, overlaped PRV-Ba and PRV-Ga labeled neurons projecting to the $B_{62}$ and $K_6$ were founded in the $A_1$ noradrenalin cells/$C_1$ adrenalin cells/caudoventrolateral reticular nucleus, rostroventrolateral reticular nuclens, nucleus tractus solitarius, area postrema, raphe obscurus nucleus, raphe paltidus nucleus, raphe magnus nucleus, lateral paragigantoceltular nucleus, lateral rcticular nucleus, gigantocellular nucleus, locus coeruleus, subcoeruleus nucleus, motor trigeminal nucleus, Kolliker-Fuse nucleus, $A_5$ cell group, central gray matter, oculomotor nerve, paraventricular hypothalamic nucleus, median eminence, amygdaloid nucleus, frontal cortex, forelimb area, hindlimb area, 1, 2 areas of parietal cortex and granular and agranular cortex. This results were suggest that overlaped PRV-Ba and PRV-Ga labeled areas projecting to the $B_{62}$ and $K_6$ may be related to the emotional relay pathway in the central autonomic center.

  • PDF

Neuroanatomical Studies on the Acupoints Related to the Large Intestine (대장(大腸)과 관련(關聯)된 경혈(經穴)들의 신경해부학적(神經解剖學的) 연구(硏究))

  • Kang, Chang-Soo;Lee, sang-ryoung;Lee, Chang-Hyun;Nam, Yong-Jae;Lee, Kwang-Gyu
    • Journal of Acupuncture Research
    • /
    • v.17 no.2
    • /
    • pp.95-117
    • /
    • 2000
  • The purpose of this morphological studies was to investigate the relation between the meridian, acupoints and viscera using neuroanatomical tracers. The common locations of the spinal ganglia, sympathetic chain ganglia, spinal cord and brain projecting to the large intestine meridian were observed following injection of transganglionic tracer, WGA-HRP and transsynaptic neurotropic virus, pseudorabies virus(PRV), Bartha strain(Ba) and PRV-Ba-Gal (Galactosidase)) into the the large intestine(cecum, colon and rectum), ST37 and LI4. After survival times of 96 hours following injection into the thirty rats with WGA-HRP, PRV-Ba and PRV-Ba-Gal. They were perfused, and their spinal ganglia, sympathetic chain ganglia, spinal cord and brain were frozen sectioned($30{\mu}m$). These sections were stained by HRP and X-gal histochemical and PRV immunohistochemical staining method, and observed with a light microscope. The results were as follows : 1. WGA-HRP labeled neurons innervating the large intestine were observed bilaterally within the T13-L4 sympathetic chain ganglia, and T9-11 spinal ganglia. WGA-HRP labeled neurons innervating ST37 were observed within the L3-5 sympathetic chain ganglia, and L2-4 spinal ganglia. WGA-HRP labeled neurons innervating LI4 were observed in the middle cervical ganglion and stellate ganglion, and C5-8 spinal ganglia. 2. In spinal cord, PRV-Ba labeled neurons projecting to the large intestine, ST37 and LI4 were found in thoracic, lumbar and sacral spinal segments. Densely labeled areas of each spinal cord segment were founded in lamina N, V, VII(intermediolateral nucleus), Ⅸ, X and dorsal nucleus. 3. In medulla oblongata, PRV-Ba and PRV-Ba-Gal labeled neurons projecting to the large intestine, ST37 and LI4 were commonly found in the A1 noradrenalin cells/C1 adrenalin cells/caudoventrolateral reticular nucleus, dorsal motor nucleus of vagus nerve, nucleus tractus solitarius, raphe obscurus nucleus, raphe pallidus nucleus, raphe magnus nucleus and gigantocellular nucleus. 4. In pons, PRV-Ba and PRV-Ba-Gal labeled neurons were commonly found in locus coeruleus, Kolliker-Fuse nucieus and A5 cell group. 5. In midbrain, PRV-Ba and PRV-Ba-Gal labeled neurons were commonly found in central gray matter. 6. In diencephalon, PRV-Ba and PRV-Ba-Gal labeled neurons were commonly found in paraventricular hypothalamic nucleus. These results suggest that PRV-Ba and PRV-Ba-Gal labeled common areas projecting to the large intestine may be correlated to that of the large intestine meridian, ST37 and LI4. Especially, These morphological results provide that interrelationship of meridian-acupoints -viscera may be related to the central autonomic pathways.

  • PDF

Localization of the Neurons Projecting to the Gallbladder Meridian (족소양담경(足少陽膽經)에서 투사(投射)되는 신경원(神經元)의 표지부위(標識部位)에 대한 연구(硏究))

  • Ryuk Sang-Won;Lee Kwang-Gyu;Lee Sang-Ryoung;Kim Jum-Young;Lee Chang-Hyun;Lee Bong-Hee
    • Korean Journal of Acupuncture
    • /
    • v.17 no.1
    • /
    • pp.101-121
    • /
    • 2000
  • The purpose of this morphological studies was to investigate the relation to the meridian, acupoint and nerve. The common locations of the spinal cord and brain projecting to the the gallbladder, GB34 and common peroneal nerve were observed following injection of transsynaptic neurotropic virus, pseudorabies virus(PRV), into the gallbladder, GB34 and common peroneal nerve of the rabbit. After survival times of 96 hours following injection of PRV, the thirty rabbits were perfused, and their spinal cord and brain were frozen sectioned($30{\mu}m$). These sections were stained by PRV immunohistochemical staining method, and observed with light microscope. The results were as follows: 1. In spinal cord, PRV labeled neurons projecting to the gallbladder, GB34 and common peroneal nerve were founded in thoracic, lumbar and sacral spinal segments. Densely labeled areas of each spinal cord segment were founded in lamina V, VII, X, intermediolateral nucleus and dorsal nucleus. 2. In medulla oblongata, The PRV labeled neurons projecting to the gallbladder, GB34 and common peroneal nerve were founded in the A1 noradrenalin cells/C1 adrenalin cells/caudoventrolateral reticular nucleus, rostroventrolateral reticular nucleus, medullary reticular nucleus, dorsal motor nucleus of vagus nerve, nucleus tractus solitarius, raphe obscurus nucleus, raphe pallidus nucleus, raphe magnus nucleus, gigantocellular nucleus, lateral paragigantocellular nucleus, principal sensory trigeminal nucleus and spinal trigeminal nucleus. 3. In Pons, PRV labeled neurons were parabrachial nucleus, Kolliker-Fuse nucleus and cochlear nucleus. 4. In midbrain, PRV labeled neurons were founded in central gray matter and substantia nigra. 5. In diencephalon, PRV labeled neurons were founded in lateral hypothalamic nucleus, suprachiasmatic nucleus and paraventricular hypothalamic nucleus. 6. In cerebral cortex, PRV labeled neuron were founded in hind limb area.This results suggest that PRV labeled common areas of the spinal cord projecting to the gallbladder, GB34 and common peroneal nerve may be first-order neurons related to the somatic sensory, viscero-somatic sensory and symapathetic preganglionic neurons, and PRV labeled common area of the brain may be first, second and third-order neurons response to the movement of smooth muscle in gallbladder and blood vessels.These PRV labeled neurons may be central autonomic center related to the integration and modulation of reflex control linked to the sensory system monitoring the internal environment, including both visceral sensation and various chemical and physical qualities of the bloodstream. The present morphological results provide that gallbladder meridian and acupoint may be related to the central autonomic pathways.

  • PDF

Central Localization of the Neurons Projecting to the Urinary Bladder Meridian (족태양방광경(足太陽膀胱經)에서 투사(投射)되는 신경원(神經元)의 표지부위(標識部位)에 대(對)한 연구(硏究))

  • Kim Jeong-Yun;Jun Hong-Jae;Lee Sang-Ryoung;Lee Chang-Hyun;Chung Ok-Bong
    • Korean Journal of Acupuncture
    • /
    • v.17 no.1
    • /
    • pp.81-100
    • /
    • 2000
  • Transsynaptic tracer이며 신경친화성 virus인 pseudorabies virus(PRV)를 방광(膀胱), 방광유(膀胱兪), 위중(委中) 및 중추(中極)에 주입(注入)한 후 4일간의 생존기간이 경과한 후 희생시켜 면역조직화학침액법(免疫組織化學染色法)에 의하여 뇌척수에 표지된 공통된 영역들을 비교하여 관찰한 결과는 다음과 같다. 1. 방광벽(膀胱壁), 방광유(膀胱兪), 위중(委中) 및 중추(中極)에서 척수에 투사된 영역은 흉수(胸髓), 요수(腰髓) 및 천수(薦髓)에 모두 표지되었으며 공통적으로 표지된 부위는 척수(脊髓)의 층판 IV, V, VII, IX, X영역에 표지되었으나 주로 강하게 표지된 공통된 영역은 층판 VII의 중간외측핵, 가슴기둥 및 층판 X영역이었다. 2. 방광벽(膀胱壁), 방광유(膀胱兪), 위중(委中) 및 중추(中極)에서 뇌(腦)에 투사된 공통된 영역은 연수(延髓)에서는 A1 noradrenalin cells/C1 adrenalin cells/caudoventrolateral reticular nucleus에서 양성반응을 나타내었다. 솔기핵의 경우 아핵인 불명솔기핵, 창백솔기핵 및 큰솔기핵에서 양성반응을 보였다. 다리뇌에서는 청색반점, Barrington's nucleus, A5세포군 및 삼차신경운동핵에서 양성반응을 보였고, 중뇌에서는 눈돌림신경핵, 눈돌림신경섬유 및 다리핵에서 양성반응을 보였다. 간뇌에서는 시상하부(視床下部)의 뇌실(腦室)곁핵과 시상의 뇌실곁핵에서 양성반응을 보였고 대뇌(大腦)에서는 septal nucleus, 피질(皮質)의 뒷다리영역, 마루엽, 이마엽에서 양성반응을 보였다. 이상의 결과를 종합하면 방광(膀胱)에서 투사되는 뇌척수의 영역과 방광유(膀胱兪)나 위중(委中)에서 투사되는 공통된 표지영역들은 방광(膀胱)과 족태양방광경(足太陽膀胱經) 그리고 그 경락(經絡)의 경혈(經穴)들이 어떤 상관성(相關性)을 가지고 연결(連結)되어 있다는 사실을 실험적으로 알 수 있었다. 특히 방광(膀胱)과 방광유(膀胱兪), 위중(委中)에서 투사된 공통된 표지영역, 즉 배뇨중추인 Barrington's nucleus에 표지되는 것은 내장(內臟)-경락(經絡)이 central autonomic pathway에 의하여 서로 연결되었음을 입증하는 중요한 결과(結果)라고 사려(思慮)된다.

  • PDF

Infectious Disease Control of Bovine Embryos (소 수정란의 전염성질병 예방)

  • 석호봉
    • Journal of Embryo Transfer
    • /
    • v.1 no.1
    • /
    • pp.16-27
    • /
    • 1986
  • Based on the current importing and exporing regulations for disease control of embryo transfer, some important microorganisms and their control possibilities are reviewed. The results reviewed were sumrnarized as follows: 1. Regulations regarding to the import of embryos vary between importing and exporting countries, but exporting countries examine the donor and embryos for the heaith certification by the requirements of importing countries. 2. Organisms that infect the gametes are 5 kinds of viruses and the diseases caused by them could not be controlled or eradicated using embryo transfer. 3. Organisms that do not infect the gametes are 4 kinds of viruses and the causal organisms are potential candidates for control or eradication by embryo transfer. 4. Organisms that penetrate the zona pellucida and infect the embryo are 6 kinds of viruses including bovine viral diarrhea virus. 5. Organisms that cannot penetrate the zona pellucida or do not infect the embryo are 15 kinds of viruses and the removal from their contaminations are recommended by proper washing procedure and antisera treatment. Bovine and porcine parvovirus, porcine pseudorabies virus and vesicular stomatitis virus are included in these organisms. 6. Bovine embryos that artificially exposed to various pathogenic organisms such as bovine herpes virus, IBR virus, bluetongue virus, bovine viral diarrhea virus and Brucella abortus in vitro are discussed about their infection by several treatments.

  • PDF

Tracing study for the rabbit eye ball control nerve utilizing the PRV-Ba isolated in the Korea (한국분리산 PRV-Ba를 이용한 가토 안구지배신경의 추적 연구)

  • Park, Il-kwon;Kim, Moo-kang;Shin, Kwang-soon;Lee, Kyung-youl;Song, Chi-won;Lee, Kang-iee;Hyun, Byung-hwa;Chang, Kyu-tae;Jeong, Young-gil
    • Korean Journal of Veterinary Research
    • /
    • v.40 no.3
    • /
    • pp.463-470
    • /
    • 2000
  • Until now peudorabies virus(PRV) has been used a neurotracer, because of it's properties of retrograde & anterograde transport. But it's anterograde transfort is not perfect, so we tested the applicability of the Bartha strain of PRV(PRV-Ba) isolated from South Korea as a neurotracer in the visual system. We performed immunohistochemical study of the rabbit brain after intravitreal injection of the PRV-Ba. After given survival time(24, 48, 72, 96, 120, 144hrs), the brain was removed and processed immunohistochemical stain for PRV-Ba. The strong PRV immunoreactivity(PRV-ir) were almost oberserved contralaterally in oculomotor neurons, fro example Edinger-Westphal nucleus, trigerminal nucleus of pons and peritrigerminal zone but locus of innervating sensitive neurons. The latter were weak positive and selective. PRV-Ba immunoreactive neurons were stained strongly in nucleus compared to cytoplasm. This study suggests that PRV-Ba isolated from South Korea is also a useful neurotracer in the motor innervated system like other PRV-strain.

  • PDF