scholarly journals Comparative Studies on Dark Adaptation in the Compound Eyes of Nocturnal and Diurnal Lepidoptera

1960 ◽  
Vol 44 (1) ◽  
pp. 195-203 ◽  
Author(s):  
C. G. Bernhard ◽  
D. Ottoson
Keyword(s):  
Comparative Analysis ◽  
Comparative Studies ◽  
Dark Adaptation ◽  
Time Course ◽  
Electrical Response ◽  
Compound Eyes ◽  
Second Phase ◽  
Nocturnal Species ◽  
Two Phases ◽  
Diurnal Species

A comparative analysis has been carried out of the time course and range of dark adaptation in the compound eyes of some common butterflies and noctuid moths (Lepidoptera). The change in sensitivity of the eye during dark adaptation was determined by measurements of the intensity of illumination necessary to elicit an electrical response of a given magnitude of the eye. It was found that the curve for dark adaptation in the diurnal species was smooth. The range of adaptive change varied in different species but usually did not cover more than 1 to 1.5 log units. In the nocturnal species the dark adaptation was found to proceed in two phases. The first phase was usually completed in less than 10 minutes and covered a range of 1 to 1.5 log units. The second phase was more prolonged and covered a range of 2 to 3 log units. In some of the experiments on nocturnal species the second phase failed to appear. Measurements of the size of the response at different intensities showed that the intensity/amplitude relationship was the same in the light-adapted eye as in the dark-adapted eye. In the nocturnal insects the response of the eye in the light-adapted condition was about 20 per cent of that in the dark-adapted eye, while in diurnal insects it was about 60 per cent.

The Sensitivity of the Ventral Nerve Photoreceptor of Limulus Recovers after Light Adaptation in Two Phases of Dark Adaptation

1986 ◽  
Vol 41 (5-6) ◽  
pp. 657-667 ◽  
Author(s):  
I. Claßen-Linke ◽  
H. Stieve
Keyword(s):  
Dark Adaptation ◽  
Time Course ◽  
Light Adaptation ◽  
Light Flash ◽  
Light Response ◽  
Receptor Potential ◽  
Second Phase ◽  
Two Phases ◽  
Ventral Nerve Photoreceptor ◽  
External Calcium

The time course of the recovery of the sensitivity of the Limulus ventral nerve photoreceptor was measured during dark adaptation following light adaptation by a bright 1 or 5 s illumination. The stimulus intensity ICR of a 300 μs light flash evoking a response of criterion amplitude (receptor potential or receptor current under voltage clamp conditions) was used as measure of sensitivity.The time course of dark adaptation shows two phases with time constants in the range of 5-9 s and 300-500 s (15 °C). Only the first of the two phases is significantly changed when the extracel- lular Ca2+-concentration is varied.The power function ICR = a·Io-tDA-b gives a good data fit for each of the two phases of dark adaptation. In the first phase the factor ax and the exponent bx are decreased when the external calcium is lowered from 10 mmol/1 to 250 μmol/1. Conversely a1 and b1 are increased when the Ca2+-concentration is raised to 40 mmol/1. For the second phase neither a2 nor b2 is changed significantly upon the changes in calcium concentration in the same experiments.The two phases of dark adaptation reflect the behaviour of the two components C1 and C2 of the electrical light response (receptor potential or receptor current). Under the conditions described here C, determines the size of the light response during the first phase of dark adaptation whereas C2 mainly influences the size of the response during the second phase.Interpretation: The fast first phase of dark adaptation is determined by the change in intracellu- lar Ca2+-concentration. The slower second phase of dark adaptation is not primarily calcium- controlled.

Visual fields of the compound eyes of four species of Cicindelidae (Coleoptera)

1980 ◽  
Vol 58 (3) ◽  
pp. 326-336 ◽  
Author(s):  
J. E. Kuster ◽  
W. G. Evans
Keyword(s):  
Visual Field ◽  
North American ◽  
Visual Fields ◽  
Morphological Characters ◽  
Head Size ◽  
Compound Eyes ◽  
Eye Size ◽  
Nocturnal Species ◽  
The Relationship ◽  
Diurnal Species

Visual field angles were measured around the circumference of the compound eyes of four species of North American Cicindelidae and plotted on Mollweide homolographs. Areas of monoscopic and stereoscopic visual fields and blind areas were calculated. In contrast to the nocturnal species (Amblycheila schwarzi and Omus californicus), the crepuscular species (Megacephala Carolina) and the diurnal species (Cicindela tranquebarica) have more ommatidia and larger eye size: head size ratios, total visual fields, and stereoscopic visual fields. These characters are considered to be derived and confirm the phylogenetic sequence of the four genera that was previously based on other morphological characters. The relationship between these characters and the biology of each species is also discussed.

scholarly journals Word Form Retrieval in Spoken Word Production

2021 ◽  
Author(s):  
◽  
Sunita Balbir Singh
Keyword(s):  
Time Course ◽  
Spoken Word ◽  
Second Phase ◽  
Young Control ◽  
Interference Task ◽  
Spoken Word Production ◽  
Two Phases ◽  
Almost All ◽  
Study Participants ◽  
Naming Latencies

<p>In the auditory picture-word interference task, participants name pictures whilst ignoring auditory distractor words. Previous studies have reported faster naming latencies when distractors are phonologically related to the target (e.g., tiger-typist) than when they are unrelated. By varying the position of overlap of the shared phonemes and the onset of the distractor, this task may provide valuable insights into the time course of phonological encoding. In the current study, participants named pictures while hearing distractor words that were: begin-related (e.g., letter-lesson); end-related (e.g., letter-otter); or unrelated to the target (e.g., letter-cabin). Distractor onsets varied from -200ms (before target) to +400ms (after target). The study was carried out in two phases: in the first phase, the task was administered to a group of 24 young control participants; in the second phase, it was administered to an individual with aphasia, NP, and a group of six older controls. Phonological facilitation effects of begin-related distractors displayed a fairly consistent pattern across the four distractor onsets for all participant groups. In almost all instances, these effects were significant but were noticeably stronger at early onsets especially around the onset of the target presentation, consistent with previous findings in the literature. Only NP showed strong begin-related facilitation effects at the latest onset. The end-related distractors however, produced somewhat different facilitation effects across the different groups. For the young controls and NP, these effects were stronger and significant at later onsets. The older controls only displayed marginally significant effects at 200ms after the target. Findings from the current study provide support for serial pattern of phoneme retrieval in multisyllabic words, in which a word‟s first syllable becomes available before later syllable(s).</p>

Gastrulation in Drosophila: the formation of the ventral furrow and posterior midgut invaginations

Development ◽  
1991 ◽  
Vol 112 (3) ◽  
pp. 775-789 ◽  
Author(s):  
D. Sweeton ◽  
S. Parks ◽  
M. Costa ◽  
E. Wieschaus
Keyword(s):  
Cell Shape ◽  
Time Course ◽  
Drosophila Embryo ◽  
Second Phase ◽  
Rapid Phase ◽  
Apical Constriction ◽  
Posterior Midgut ◽  
Ventral Furrow ◽  
Two Phases ◽  
Shape Changes

The ventral furrow and posterior midgut invaginations bring mesodermal and endodermal precursor cells into the interior of the Drosophila embryo during gastrulation. Both invaginations proceed through a similar sequence of rapid cell shape changes, which include apical flattening, constriction of the apical diameter, cell elongation and subsequent shortening. Based on the time course of apical constriction in the ventral furrow and posterior midgut, we identify two phases in this process: first, a slow stochastic phase in which some individual cells begin to constrict and, second, a rapid phase in which the remaining unconstricted cells constrict. Mutations in the concertina or folded gastrulation genes appear to block the transition to the second phase in both the ventral furrow and the posterior midgut invaginations.

Time-course of release and synthesis of luteinizing hormone, follicle-stimulating hormone and prolactin from rat pituitary glands in vitro

1983 ◽  
Vol 96 (2) ◽  
pp. 165-170 ◽  
Author(s):  
Marta E. Apfelbaum
Keyword(s):  
Time Course ◽  
Ovariectomized Rats ◽  
Second Phase ◽  
Hormone Synthesis ◽  
Continuous Release ◽  
Rat Pituitary ◽  
Pituitary Glands ◽  
Secondary Phenomenon ◽  
Two Phases

To study the time-course of release and synthesis of LH, FSH and prolactin, anterior pituitary glands from ovariectomized rats were incubated for different time-intervals between 0 and 4 h. Comparable patterns of release and synthesis of LH and FSH as a function of the incubation time were observed. It was possible to distinguish two phases in the profiles of secretion of both gonadotrophins. During the first phase, from 0–2 h, release was associated with a corresponding decrease of the hormone concentrations within the gland but no overall changes in total LH and FSH production. During the second phase, between 2 and 4 h, a progressive reaccumulation of both gonadotrophins occurred in spite of the continuous release of hormones into the medium, reflecting formation of new immunoassayable material. These results suggest that the increased synthesis ensues as a secondary phenomenon arising from the release of the hormones from the tissue. The time-course of release and synthesis of prolactin showed different dynamics during the course of incubation. High levels of prolactin were released and synthesized when the adenohypophysis was incubated in vitro. Considerably larger amounts of this hormone were found in the medium than in the tissue from the first hour of incubation. After a lag of about 40 min synthesis of prolactin was increased in parallel with its release. This led to the assumption that both prolactin synthesizing and releasing processes occurred simultaneously from the early stages of the incubation. Comparatively, prolactin-secreting cells had a very fast and LH-secreting cells a low rate of turnover; FSH-secreting cells were intermediate between the two. These results indicate that (1) the increase in release of LH, FSH and prolactin into the medium precedes that of hormone synthesis and (2) the initial depletion of the pituitary gland as a result of hormone release could act as a stimulus for synthesis, leading to the reestablishment of hormonal storage levels.

scholarly journals Emergence of Multi-Drug Resistant Clinical Strains of Staphylococcus aureus

2016 ◽  
pp. 1-6
Author(s):  
B Saha ◽  
M Bal
Keyword(s):  
Staphylococcus Aureus ◽  
Comparative Analysis ◽  
Methicillin Resistance ◽  
Aureus Strain ◽  
Resistance Pattern ◽  
Second Phase ◽  
Drug Resistant ◽  
Clinical Strains ◽  
Significant Difference ◽  
Two Phases

Indiscriminate and wide spread use of antibiotics has lead to the development of multi-drug-resistant strains of pathogenic Staphylococcus aureus. Information regarding increase (in percentage) of existing resistance as well as emergence of new resistance to different antibiotics used for staphylococcal infections are insufficient. This study explores a comparative analysis of growing resistance to different antibiotics mainly ampicillin, methicillin, erythromycin, gentamicin, clindamycin and vancomycin against S. aureus isolated from Kolkata hospitals during two phases. During first phase (126) and second phase (67) non-repeat clinical strains of S. aureus obtained from different hospitals of Kolkata were identified by standard biochemical methods. However, PCR amplification of nuc gene and rDNA was also performed for identification of S. aureus. Antibiotic susceptibility pattern was determined by Disc Agar Diffusion tests and mecA was identified by PCR. Comparative analysis of antibiotic resistance pattern of the strains isolated during two phases showed significant difference (p=0.05) with 75% increase of resistance to erythromycin followed by 30% increase to ampicillin, chloramphenicol and streptomycin with the appearance of vancomycin resistance. Gentamicin and methicillin resistance have increased by 22% and 7% respectively. On the other hand, mecA was obtained by PCR from vancomycin resistant S. aureus strain, which was also resistant to methicillin, erythromycin and clindamycin. This study reveals tremendous increase of resistance to erythromycin and a remarkable increase to other antibiotics with emergence of multidrug- resistant clinical strains of S. aureus. This trend in increasing resistance to the commonly used antibiotics against S. aureus cannot be controlled until and unless antibiotics are used more prudently.International Journal of Natural Sciences (2013), 3(1-4) 1-6

scholarly journals Word Form Retrieval in Spoken Word Production

2021 ◽  
Author(s):  
◽  
Sunita Balbir Singh
Keyword(s):  
Time Course ◽  
Spoken Word ◽  
Second Phase ◽  
Young Control ◽  
Interference Task ◽  
Spoken Word Production ◽  
Two Phases ◽  
Almost All ◽  
Study Participants ◽  
Naming Latencies

<p>In the auditory picture-word interference task, participants name pictures whilst ignoring auditory distractor words. Previous studies have reported faster naming latencies when distractors are phonologically related to the target (e.g., tiger-typist) than when they are unrelated. By varying the position of overlap of the shared phonemes and the onset of the distractor, this task may provide valuable insights into the time course of phonological encoding. In the current study, participants named pictures while hearing distractor words that were: begin-related (e.g., letter-lesson); end-related (e.g., letter-otter); or unrelated to the target (e.g., letter-cabin). Distractor onsets varied from -200ms (before target) to +400ms (after target). The study was carried out in two phases: in the first phase, the task was administered to a group of 24 young control participants; in the second phase, it was administered to an individual with aphasia, NP, and a group of six older controls. Phonological facilitation effects of begin-related distractors displayed a fairly consistent pattern across the four distractor onsets for all participant groups. In almost all instances, these effects were significant but were noticeably stronger at early onsets especially around the onset of the target presentation, consistent with previous findings in the literature. Only NP showed strong begin-related facilitation effects at the latest onset. The end-related distractors however, produced somewhat different facilitation effects across the different groups. For the young controls and NP, these effects were stronger and significant at later onsets. The older controls only displayed marginally significant effects at 200ms after the target. Findings from the current study provide support for serial pattern of phoneme retrieval in multisyllabic words, in which a word‟s first syllable becomes available before later syllable(s).</p>

Time Course of Active Amylase Accumulation by Rat Submaxillary Gland During Continuous Pilocarpine Stimulation

1957 ◽  
Vol 189 (1) ◽  
pp. 129-131 ◽  
Author(s):  
Charlotte A. Schneyer ◽  
Leon H. Schneyer
Keyword(s):  
Time Course ◽  
Submaxillary Gland ◽  
Enzyme Synthesis ◽  
Second Phase ◽  
Enzyme Form ◽  
Submaxillary Glands ◽  
Autocatalytic Process ◽  
Wet Weight ◽  
Two Phases

Administration of pilocarpine for varying periods results in a continuous orderly increase in the amylase levels of rat submaxillary glands without prior depletion or accompanying appreciable changes in gland wet weight. This amylase increase with time appears to occur in two phases: the first phase is characterized by a possible brief initial lag followed by a period of logarithmic increase leading to a plateau within 90 minutes. A second phase of rapid rise occurs within 3 hours. The S-shaped curve of the first phase suggests the time course of an autocatalytic process and may indicate a) synthesis, or b) activation of a precursor or bound enzyme form. Sodium oleate, urea, trypsin, n-butanol, heat and ph activate precursors of other enzymes but neither activated nor significantly inhibited amylase of gland homogenates. Atropine in vivo effected complete inhibition of the pilocarpine-induced amylase accumulation. Amylase accumulation under these conditions suggests enzyme synthesis.

Effect of Calcium ion on the interaction between Thrombin and Heparin. Thermal Denaturation

1977 ◽  
Vol 38 (03) ◽  
pp. 0677-0684 ◽  
Author(s):  
Raymund Machovich ◽  
Péter Arányi
Keyword(s):  
Calcium Ions ◽  
Rate Constants ◽  
Thermal Denaturation ◽  
Time Course ◽  
Complex Analysis ◽  
Heat Inactivation ◽  
Second Phase ◽  
Denaturation Kinetics ◽  
Enzyme Protection ◽  
Enzyme Denaturation

SummaryHeat inactivation of thrombin at 54° C followed first order kinetics with a rate constant of 1.0 min−1 approximately. Addition of heparin resulted in protection against thermal denaturation and, at the same time, rendered denaturation kinetics more complex. Analysis of the biphasic curve of heat inactivation in the presence of heparin revealed that the rate constants of the second phase changed systematically with heparin concentrations. Namely, at 4.5 × 10−6M, 9 × 10−6M, 1.8 × 10−5M and 3.6 × 10−5M heparin concentrations, the rate constants were 0.27 min−1, 0.17 min−1, 0.11 min−1 and 0.06 min−1, respectively.Sulfate as well as phosphate ions displayed also enzyme protection against heat inactivation, however, the same effect was obtained already at a heparin concentration, lower by three orders of magnitude.The kinetics of enzyme denaturation was not affected by calcium ions, whereas in the presence of heparin the inactivation rate of thrombin changed, i. e. calcium ions abolished the biphasic character of time course of thermal denaturation.Thus, the data suggest that calcium ions contribute to the effect of heparin on thrombin.

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