Birdsong, like human speech, consists of a sequence of temporally precise movements acquired through vocal learning. The learning of such sequential vocalizations depends on the neural function of the motor cortex and basal ganglia. However, it is unknown how the connections between cortical and basal ganglia components contribute to vocal motor skill learning, as mammalian motor cortices serve multiple types of motor action and most experimentally tractable animals do not exhibit vocal learning. Here, we leveraged the zebra finch, a songbird, as an animal model to explore the function of the connectivity between cortex-like (HVC) and basal ganglia (area X), connected by HVC(X) projection neurons with temporally precise firing during singing. By specifically ablating HVC(X) neurons, juvenile zebra finches failed to copy tutored syllable acoustics and developed temporally unstable songs with less sequence consistency. In contrast, HVC(X)-ablated adults did not alter their learned song structure, but generated acoustic fluctuations and responded to auditory feedback disruption by the introduction of song deterioration, as did normal adults. These results indicate that the corticobasal ganglia input is important for learning the acoustic and temporal aspects of song structure, but not for generating vocal fluctuations that contribute to the maintenance of an already learned vocal pattern.
Apoptosis is the process of programmed cell death (PCD) which usually occurs in multicellular organisms. In this case, biochemical events leads to morphological cell changes and death. Some of these changes are blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation and chromosomal Deoxyribonucleic Acid (DNA) fragmentation. Apoptosis is however distinct from necrosis which is a form of traumatic cell death that results from acute cellular injury. Apoptosis generally confers advantages during an organism's life cycle. One of the advantages can be seen in the differentiation of fingers and toes in a developing human embryo. This occurs because cells between the fingers apoptose and causes the digits to be separate. Unlike necrosis, apoptosis produces cell fragments called apoptotic bodies that phagocytic cells are able to engulf and quickly remove before the contents of the cell can spill out onto surrounding cells and cause damage. Also, between 50 and 70 billion cells die each day due to apoptosis in the average human adult. For an average child between the ages of 8 and 14, approximately 20 billion to 30 billion cells die a day.. In addition to its importance as a biological phenomenon, defective apoptotic processes have been implicated in an extensive variety of diseases whereby excessive apoptosis causes atrophy and an insufficient apoptosis results in uncontrolled cell proliferation leading to cancer or tumour
Bitter cola (Garcinia kola) powder and its ethanolic extract were assessed for their ability to inhibit the growth of a wild strain of Saccharomyces cerevisiae isolated from a brewery environment. The iso-alpha acid contents of the G. kola powder, G. kola extract and hop extract were determined as 5.85 mg/l, 6.34 mg/l and 7.65 mg/l, respectively, showing that the iso-alpha acid contents of G.
kola extract and G. kola powder compared relatively well with that of hop extract. The antimicrobial activity of both agents, using Humulus lupulus ethanolic extract as control, showed a high dependence on the temperature of assay. At most of the temperatures evaluated (30 -45 o C), the rates of antimicrobial activity differed. Garcinia kola ethanolic extract and hops extract displayed total inhibition of the wild yeast growth at temperature of 40 o C at concentrations of about 0.039 mg/ml and 0.078 mg/ml respectively. Humulus lupulus extract (hops) had the highest generation time at 450 C at a concentration of 0.078 mg/ml. The complete inhibition of the yeast growth by G. kola extract at 40 o C indicated that it had higher antimicrobial activity against this yeast than hops extract. In all the temperatures evaluated both G. kola ethanolic extract and powder compared favourably with hops extract with respect to antimicrobial activity against a wild strain of Saccharomyces cerevisiae at various concentrations. These results revealed that the antimicrobial activity of these hopping agents were temperature and concentration dependent.
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