• Bulletin of the Korean Chemical Society
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• v.27 no.7
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• pp.1015-1019
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• 2006

The peptide with structural similarity to mammalian substance P (M-SP) has been isolated from extract of the body of the African lungfish, Protopterus dolloi, using the rectum of the newt as the bioassay system. The primary structure of the SP-related peptide was identified as Lys-Pro-Arg-Pro-Asp-Gln-Phe-Tyr-Gly-Leu-Met-NH2 (L-SP) and contained four substitutions ($Lys^{1}\rightarrow $ Arg, $Arg^{3}\rightarrow$ Lys, $Asp^{5}\rightarrow$ Gln, and $Tyr^{8}\rightarrow$ Phe) compared with M-SP; this structure is identical to that of the peptide isolated from the gut of the Australian lungfish. Circular dichroism spectra showed that L-SP had an unordered structure in the buffer solution and phospholipid bilayers. This peptide was found to have an excitatory effect on rectal muscle tissues of newt, quail, and fish. L-SP also had a more potent vasodilatory effect on the guinea-pig aorta than that of M-SP. The identification of the peptide provides evidence that SP family, hitherto confined to mammals, have a widespread occurrence in lungfish.

• Bulletin of the Korean Chemical Society
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• v.27 no.11
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• pp.1733-1736
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• 2006

A new biologically active peptide with structural similarity to neuromedin N (NMN) has been isolated from extracts of visceral tissue of the African lungfish, Protopterus dolloi, using the rectum of the quail as the bioassay system. The primary structure of NMN-related peptide was established as Lys-Ala-Pro-Tyr-Ile-Leu-OH ([$Ala_2$]-NMN) and contained one substitution ($Ala_2\rightarrow$Ile) compared with the porcine NMN. [$Ala_2$]-NMN was found to have an excitatory effect on rectal muscle tissues of quail (Coturnix japonica), newt (Cynops pyrrhogaster) and black bass (Micropterus sulmoides). The threshold concentration of [Ala2]-NMN for contraction of C. japonica muscle was found to be approximately $10^-11$M. [$Ala_2$]-NMN showed contractile activities in the following order: C. japonica > C. pyrrhogaster > M. sulmoides. The identification of [Ala2]-NMN provides evidence that NMN family, hitherto confined to mammals, has a widespread occurrence in lungfish.

• Journal of Aquaculture
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• v.15 no.1
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• pp.43-48
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• 2002

We investigated the gonadosomatic index (GSI), germ cell development, reproductive cycle of the Afriean lungfish Protorierus annecteus (Owen) by histological observations and morphometric data. Samples were collected from the river Orie and its flood of Nigeria, from January to December 2000. The fish is dioecious and oviparous. Monthly changes in the gonadosomatic index (GSI) showed a similar pattern to change in the mean oocyte diameter and the reproductive cycle. The reproductive period occurred from March to July-August; the spawning period was once a year between truly and August, and the main spawning occurred in August when active and voracious feeding occurred during the rainy season. In the resting (dormant) stage after spawning, fish stopped feeding and aestivated during the dry season from December to February. The reproductive cycle of the species can be divided into five successive stages, quiescent stage (March to April), developing/maturing stage (April to lune), ripe/spawning stage (July to August), post-spawning stage (September to November), and resting (dormant) stage (December to February).

• Journal of Aquaculture
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• v.14 no.2
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• pp.73-79
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• 2001

Testicular development of the male African lungfish, Protopterus annectens (Owen) was investigated histologically. The testis was found to be an elongated structure that possessed two distinct portions: an anterior spermatogenic part that was made up of a system of testicular tubules and a posterior vesicular part that invaded the kidney tissue. Spermatogenesis can be divided into five stages; primary spermatogonia, secondary spermatogonia, spermatocyte, spermatids and spermatozoa. Based on the gonadosomatic index (GSI) and histological changes observed, the reproductive cycle can be divided onto four distinct stages: resting and quiescent (December to February), growing (March to June) ripe and spent (July to August) and postspawning (September to November). The GSI was the maximum on July when reproductive cells were mature, ripe and ready for spawning; and the minimum in August after fish spawned.

• Applied Microscopy
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• v.51
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• pp.5.1-5.7
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• 2021

The olfactory organs of two African lungfishes, Protopterus amphibius and P. dolloi, were investigated using a stereo microscope and a compound light microscope and were described anatomically, histologically, and histochemically. Like other lungfishes, these species present the following general features: i) elongated olfactory chamber (OC), ii) anterior nostril at the ventral tip of the upper lip, iii) posterior nostril on the palate of the oral cavity, iv) lamellae with multiple cell types such as olfactory receptor neurons, supporting cells, basal cells, lymphatic cells, and mucous cells (MC), and vi) vomero-like epithelial crypt (VEC) made of glandular epithelium (GE) and crypt sensory epithelium. Some of these features exhibit differences between species: MCs are abundant in both the lamellar and inner walls of the OC in P. amphibius but occur only in lamellae in P. dolloi. On the other hand, some between feature differences are consistent across species: the GE of both P. amphibius and P. dolloi is strongly positive for Alcian blue (pH 2.5)-periodic acid Schiff (deep violet coloration), and positive with hematoxylin and eosin and with Masson's trichrome (reddish-brown staining), unlike the MCs of the two species which stain dark red with both Alcian blue (pH 2.5)-periodic acid Schiff and Masson's trichrome but respond faintly to hematoxylin and eosin. The differing abundance of MCs in the two lungfishes might reflect different degrees in aerial exposure of the olfactory organ, while the neutral and acid mucopolysaccharide-containing VEC, as indicated by staining properties of the MCs, is evolutionary evidence that P. amphibius and P. dolloi are the closest living relatives to tetrapods, at least in the order Dipnoi.