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Telomeres comprise tandem repeated DNA sequences that protect the ends of chromosomes from deterioration or fusion with neighboring chromosomes, and their lengths might vary with sex and age. Here, age‐ and sex‐related telomere lengths in male and female captive Siamese cobras (Naja kaouthia) were investigated using quantitative real‐time polymerase chain reaction based on cross‐sectional data. A negative correlation was shown between telomere length and body size in males but not in females. Age‐related sex differences were also recorded. Juvenile female snakes have shorter telomeres relative to males at up to 5 years of age, while body size also rapidly increases during this period. This suggests that an accelerated increase in telomere length of female cobra results from sex hormone stimulation to telomerase activity, reflecting sexually dimorphic phenotypic traits. This might also result from amplification of telomeric repeats on sex chromosomes. By contrast, female Siamese cobras older than 5 years had longer telomeres than males. Diverse sex hormone levels and oxidative stress parameters between sexes may affect telomere length.

Characterizing and comparing developmental progress across different species helps to interpret how different or similar body forms evolved. We present an embryonic table for the oviparous African Sand Snake Psammophis sibilans from the Lamprophidae family, describing its postovipositional in ovo development. Psammophis is a good model of a genus that is widely distributed in Africa and Asia and includes 22 species. We describe ten embryonic stages based on the development of externally visible morphological characteristics such as; pharyngeal arches, facial processes, eyes, scales, body pigmentation and body colour pattern development. This study discusses the development of this snake and compares it with that of the closely related brown house snake Lamprophis fulliginosus (Lamprophidae) and the medically important venomous cobras Naja haje haje and Naja kaouthia from the sister lineage Elapidae. The distantly related basal snake Python sebae, which displays different morphology and behaviour, was chosen for deeper insight into the evolution of body structures within the snake clade. We found interspecific differences in the relative stage of development of embryonic structures at the time of oviposition and during postovipositional embryonic development. One of the outcomes of this study is that embryonic structures such as the pharyngeal processes, eye pigmentation and scales are interspecifically conservative in regard to timing of morphodifferentiation, while body pigmentation, colour and colour pattern are interspecifically plastic in their temporospatial development.

Snake venom three finger toxins (3FTxs) are a non-enzymatic family of venom proteins abundantly found in elapids. We have purified a 7579.5 ± 0.591 Da 3FTx named as Nk-3FTx from the venom of Naja kaouthia of North East India origin. The primary structure was determined by a combination of N-terminal sequencing and electrospray ionization liquid chromatography-mass spectrometry/mass spectrometry. Biochemical and biological characterization reveal that it is nontoxic to human cell lines and exhibit mild anticoagulant activity when tested on citrated human plasma. Nk-3FTx was found to affect the compound action potential (CAP) and nerve conduction velocity of isolated toad sciatic nerve. This is the first report of a non-conventional 3FTx from Naja kaouthia venom that reduces CAP for its neurotoxic effect. Further studies can be carried out to understand the mechanism of action and to explore its potential therapeutic application.

The Egyptian cobra, Naja h. haje, is the largest of the African cobras and is a member of a successful and medically important species complex found throughout Africa, north and south of the Sahara, as well as across the Arabian Peninsula to Oman. Although its phylogenetic position and venom characteristics have been well studied, its development has not. Here, we present a normal staging table for N. h. haje, based on external features. Comparison with firstly the Asian monocled cobra, Naja kaouthia, and then with the small number of other oviparous snake species, allowed us to examine whether differences between two species in the same genus were of the same type and magnitude as those between unrelated genera. In fact, at least with respect to external features, we found a similar level of disparity. N. h. haje embryos lagged behind those of N. kaouthia in body and head scale development, size in ovo and hatchling length, despite having a slightly shorter incubation period and a somewhat larger adult size. Some of these differences may have been the result of differing incubation temperatures. Nonetheless, there does appear to be a broadly conserved pattern of in ovo development in at least macrostomatan snakes.

Rediocides A and G, the principle components of Trigonostemon reidioides (Kurz) Craib, which is known as Lotthanong in Thai, were investigated for a detoxification mechanism against Naja kaouthia venom by in silico, in vitro, and in vivo methods. Molecular dockings of alpha-cobratoxin with rediocides A and G were performed, and the binding energies were found to be -14.17 and -14.14 kcal/mol, respectively. Rediocides bind to alpha-cobratoxin at the same location as alpha-cobratoxin binds to the nicotinic acetylcholine receptor (nAChR), i.e., at the Asp27, Phe29, Arg33, Gly34, Lys35, and Val37 residues. alpha-Cobratoxin cannot bind to nAChR, because some of its binding sites are occupied with rediocides. From in vitro SDS-PAGE, it was found that rediocides can diminish the bands of alpha-cobratoxin. In the presence of acetylcholine-binding protein (AChBP), it was apparent that rediocides can bind both alpha-cobratoxin and AChBP. From an in vivo test, it was found that injection of rediocides at 0.5 mg/kg immediately after an alpha-cobratoxin dose of three times LD(50) cannot prolong the survival time of mice. However, rediocide can prolong the survival time, if it is injected 30 min before the injection of alpha-cobratoxin. The in vitro SDS-PAGE and the in vivo results support the in silico detoxification mechanism of rediocides against cobra venom at a molecular level.

Weak neurotoxins belong to the superfamily of three-finger toxins from snake venoms. In general, weak toxins have a low toxicity and, contrary to other three-finger toxins, their molecular targets are not well characterized: in vitro tests indicate that these may be nicotinic acetylcholine receptors. Here, we report the influence of intraperitoneal and intravenous injections of weak neurotoxin from Naja kaouthia venom on mouse behaviour. Dose-dependent suppression of orientation-exploration and locomotion activities as well as relatively weak neurotropic effects of weak neurotoxin were observed. The myorelaxation effect suggests a weak antagonistic activity against muscle-type nicotinic acetylcholine receptors. Neurotoxic effects of weak neurotoxin were related to its influence on peripheral nervous system. The symptomatology of the intoxication was shown to resemble that of muscarinic agonists. Our data suggest that, in addition to interaction with nicotinic acetylcholine receptors observed earlier in vitro, weak neurotoxin interacts in vivo with some other molecular targets. The results of behavioural experiments are in accord with the pharmacological profile of weak neurotoxin effects on haemodynamics in mice and rat indicating the involvement of both nicotinic and muscarinic acetylcholine receptors.

Selective cloning of the cDNA coding for a weak neurotoxin (WTX) from cobra N. kaouthia including the 5'- and 3'-non-translated regions (NTR) is described. The known amino acid sequence of WTX was used together with the nucleotide sequence of a weak neurotoxin NNAM2 from cobra Naja atra, to design WTX-specific primers for direct amplification of an internal WTX cDNA fragment by RT- PCR. The sequence of the complete WTX cDNA was determined in sequencing runs on internal PCR products, cloned 3'- and 5'-RACE-fragments and several full-length cDNA clones. The cDNA coding sequence is in excellent agreement with the previously determined WTX amino acid sequence, has a high homology with other known weak toxin cDNAs, whereas even higher homology (up to 96%) with several classes of 3-finger toxins was detected in the 59 bp 3'-NTR consensus sequence. A possible function of the highly conserved nucleotide sequence elements is discussed.