S100A2 in cancerogenesis: a friend or a foe?

Owing to the exceptional intracellular distribution and the heterogeneous expression pattern during transformation and metastasis in various tumors, the EF-hand calcium-binding protein S100A2 attracts increasing attention. Unlike the majority of S100 proteins, S100A2 expression is downregulated in many cancers and the loss in nuclear expression has been associated with poor prognosis. On the other hand, S100A2 is upregulated in some cancers. This mini review highlights the general characteristics of S100A2 and discusses recent findings on its putative functional implication as a suppressor or promoter in cancerogenesis.     

The cortical response in Xenopus laevis ova

A dependence on extracellular calcium has been demonstrated for fertilization and the cortical response to pricking in Xenopus ova. Neither event occurred in calcium-free solutions or in the presence of divalent cation chelating agents. The calcium-sensitive phase of the cortical response to pricking in dejellied eggs was restricted to the 5–10 sec immediately following the activation stimulus; the initial phase of activation was not calcium dependent. In contrast, the cortical response in dejellied Xenopus ova exposed to the chemical activating agents, urethan or methyl urethan, was independent of extracellular calcium. Experimental evidence was presented for the involvement of a direct, nonpropagated cortical reaction in response to urethan stimulation as opposed to a propagated reaction in response to pricking. A cortical response in dejellied eggs was not induced spontaneously by high concentrations of potassium, and the prick response was unaffected by inhibitors of energy transfer processes. Molecular mechanisms operative in the initiation and propagation of the cortical response in animal eggs have been discussed.     

Identification of a male-specific (H-Y) antigen on the flagellar plasma membrane of ram epididymal spermatozoa

Summary H-Y (male-specific) antigen has been detected on the plasma membranes of both caput and caudal ram spermatozoa using both immunoperoxidase and immunofluorescence labelling techniques. In these spermatozoa the distribution of H-Y antigen appears to be confined to both the posterior region of the head and the mid-piece region of the flagellum. In addition, caput spermatozoa also exhibit intense immunoperoxidase staining of the cytoplasmic droplet which is situated on the flagellum at the base of the head. Western blot analyses of purified plasma membranes from the flagella of caudal spermatozoa have revealed the presence of a malespecific protein with an estimated molecular weight of 25,000–27,000.     

Isolation and Pathogenicity of Rhizosphere Fungi of Cocoyam in Relation to Cocoyam Root Rot Disease

Cocoyam is the second most important staple crop of Cameroon and root rot is a destructive disease of this plant. Pythium myriotylum (Pm), Fusarium solani (Fs), and Rhizoctonia solani (Rs) were isolated from the rhizosphere of root rot affected cocoyams and from the soil of a cocoyam experimental field plot temporarily devoid of same in Mamu, Cameroon. Pm was isolated from the above soil by the cocoyam leaf disc baits. Fs and Rs were also isolated from the same soils by the water dilution method and from the roots of diseased cocoyams but were always associated with mycelial growth of Pm. Pathogenicity of Pm and in combinations with Fs or Rs or Fs + Rs all developed cocoyam root rot disease (CRRD) symptoms on 3– and 7–month old cocoyam plantlets 2–7 days after inoculation. Symptoms included rotted roots and wilting with general chlorosis of inoculated plantlets. No symptoms of CRRD were noted on cocoyam plantlets inoculated with Fs, Rs, Fs + Rs, and distilled water. Results indicated that CRRD is not caused by several pathogens but only by Pm. Pm isolates from the soils and roots of diseased cocoyams and those maintained in the ROTREP laboratory have significantly bigger diameter of mycelial colony growth in 24 h–period at 31 °C on lima bean sucrose agar, V–8 juice sucrose agar, and potato sucrose agar than on potato dextrose agar and 2 % water agar. The cocoyam plantlets were raised axenically from tissue culture of explants in the laboratory.     

Circum-Antarctic continental distribution patterns in pteridophyte species

Four major austral continental distribution patterns are evident in pteridophytes. Twenty-two species are completely circum-Antarctic. Another 39 species are partially circum-Antarctic, occurring in Australasia (Australia and New Zealand) and Africa (including Madagascar) but not South America, while 29 are in Africa and South America but not Australasia, and 13 are in South America and Australasia but not Africa. Two hypotheses are considered as explanations for the patterns: continental drift following the breakup of Gondwana and long-distance dispersal. Fossil evidence indicates that the majority of pteridophyte families involved appeared after the southern continents had drifted apart, so long-distance dispersal is likely to explain the distribution of species in these families on now widely separated continents. For those families extant before the break-up, there is no indication in the fossil record that the species involved were present in Gondwana. Aspects of the ecology of the species that are partly or completely circum-Antarctic indicate that long-distance dispersal, rather than continental drift, is a likely explanation for the patterns.     

Learning to Produce Syllabic Speech Sounds via Reward-Modulated Neural Plasticity

At around 7 months of age, human infants begin to reliably produce well-formed syllables containing both consonants and vowels, a behavior called canonical babbling. Over subsequent months, the frequency of canonical babbling continues to increase. How the infant’s nervous system supports the acquisition of this ability is unknown. Here we present a computational model that combines a spiking neural network, reinforcement-modulated spike-timing-dependent plasticity, and a human-like vocal tract to simulate the acquisition of canonical babbling. Like human infants, the model’s frequency of canonical babbling gradually increases. The model is rewarded when it produces a sound that is more auditorily salient than sounds it has previously produced. This is consistent with data from human infants indicating that contingent adult responses shape infant behavior and with data from deaf and tracheostomized infants indicating that hearing, including hearing one’s own vocalizations, is critical for canonical babbling development. Reward receipt increases the level of dopamine in the neural network. The neural network contains a reservoir with recurrent connections and two motor neuron groups, one agonist and one antagonist, which control the masseter and orbicularis oris muscles, promoting or inhibiting mouth closure. The model learns to increase the number of salient, syllabic sounds it produces by adjusting the base level of muscle activation and increasing their range of activity. Our results support the possibility that through dopamine-modulated spike-timing-dependent plasticity, the motor cortex learns to harness its natural oscillations in activity in order to produce syllabic sounds. It thus suggests that learning to produce rhythmic mouth movements for speech production may be supported by general cortical learning mechanisms. The model makes several testable predictions and has implications for our understanding not only of how syllabic vocalizations develop in infancy but also for our understanding of how they may have evolved.