Regulation of shell growth in the pulmonate gastropod Helisoma duryi

1978 ◽  
Vol 56 (9) ◽  
pp. 1975-1980 ◽  
Author(s):  
S. C. Kunigelis ◽  
A. S. M. Saleuddin
Keyword(s):  
Shell Growth ◽  
Relative Proportion ◽  
Continuous Light ◽  
Continuous Darkness ◽  
Deposition Rates ◽  
Factors Affecting ◽  
Helisoma Duryi ◽  
Shell Deposition ◽  
Slow Growing ◽  
Pulmonate Gastropod

Photoperiod has a significant effect on linear shell deposition rates; animals maintained in continuous darkness (DD) deposit shell more rapidly than those held in continuous light (LL) or 12L: 12D. Shell deposition is endogenously governed and might be synchronized by photoperiod. Photoperiod also affects the relative proportion of shell occupied by different crystal layers.Injections of brain homogenates from fast-growing animals stimulate shell deposition in slow-growing animals. Supraoesophageal and suboesophageal brain fractions both have a greater effect than whole brain; both fractions may contain factors affecting shell growth. Suboesophageal fractions from shell-repairing donors show a reduced effect. A supraoesophageal factor may be involved in normal shell growth and a suboesophageal factor in shell repair.

Factors affecting perithecial production in Gibberella (Fusarium) tricincta

1979 ◽  
Vol 57 (22) ◽  
pp. 2497-2500 ◽  
Author(s):  
N. E. El-Gholl ◽  
C. L. Schoulties ◽  
W. H. Ridings
Keyword(s):  
Mass Culture ◽  
Basal Medium ◽  
Continuous Light ◽  
Colony Growth ◽  
Constant Darkness ◽  
Continuous Darkness ◽  
Hedera Helix ◽  
Pigment Formation ◽  
Factors Affecting ◽  
Leaf Spots

Three pigmentation types (brown, red, and white) of Fusarium tricinctum (Corda) Sacc. were observed when an isolated mass culture from leaf spots on English ivy (Hedera helix L.) was single spored. Perithecia of the heterothallic fungus Gibberella tricincta El-Gholl were produced at 20 and 27 °C on stem pieces of Cynodon dactylan Pers. resting on water agar, under 12-h alternating light and dark when certain pigmentation types were paired. Pairing of red and brown pigmentation types yielded significantly (P < 0.05) more perithecia than red and white pairings at 20 and 27 °C. Perithecia were formed only in combinations of red with brown or white pigmentation types. In both sets of pairings, significantly (P < 0.05) more perithecia were produced at 27 than at 20 °C. No perithecia were formed in constant darkness. Occasionally, the red pigmentation type became white after subsequent transfers and never reverted to the red pigmentation on various media and failed to produce perithecia with any pigmentation type. Continuous darkness slightly favored red pigment formation over continuous light as detected by the Munsell color codes. Increasing temperatures from 20 to 32 °C decreased the colony growth diameter of the red-pigmented cultural type. At 32 °C a change in hue was noted with corresponding changes in color codes. Red mycelial pigmentation was intensified by the addition of copper, iron, manganese, and zinc to a basal medium. The addition of 0.1% yeast extract favored mycelial development and caused a more pronounced red mycelial pigmentation in the presence of heavy metals.

Studies on the in vitro formation of periostracum in Helisoma duryi: the influence of the dorsal epithelium on calcium incorporation

1984 ◽  
Vol 62 (6) ◽  
pp. 1177-1180 ◽  
Author(s):  
S. C. Kunigelis ◽  
A. S. M. Saleuddin
Keyword(s):  
Epithelial Tissue ◽  
Whole Brain ◽  
Fast Growing ◽  
Cerebral Ganglia ◽  
Helisoma Duryi ◽  
Shell Deposition ◽  
Slow Growing

Mantle collar tissue was found to produce periostracum when placed in vitro. The rate of shell deposition in vivo was reflected in the in vitro rate of periostracum formation. The addition of whole brain from fast-growing donors to mantle collar from slow-growing animals was found to increase the amount of periostracum produced in vitro. This effect was further enhanced by removing the cerebral ganglia lateral lobes prior to incubation. The presence of dorsal epithelial tissue was found to increase the incorporation of calcium into periostracum formed in vitro.

scholarly journals Factors affecting adventitious root formation in isolated stem segments of Rhododendron.

1969 ◽  
Vol 17 (3) ◽  
pp. 203-208
Author(s):  
R.L.M. Pierik
Keyword(s):  
Mineral Nutrition ◽  
Adventitious Root ◽  
Culture Medium ◽  
Root Formation ◽  
Continuous Light ◽  
Adventitious Root Formation ◽  
Continuous Darkness ◽  
Factors Affecting ◽  
Stem Segments

Stem expiants of the rhododendron cultivar Catawbiense Album rooted more easily in vitro than those of Pink Pearl, agreeing with the experience of nursery practice. Rooting occurred only on segments of young soft shoots and was strongly promoted when the expiants were placed inverted on the medium. Continuous light inhibited, whereas continuous darkness promoted rooting. Rooting occurred only in the presence of an auxin together with a sugar in the culture medium. There was no evidence that mineral nutrition and temperatures between 21 degrees and 29 degrees C. play an important role.-Univ. Wageningen. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Environmental and nutritional factors affecting the in vitro inhibition of the vegetative growth of Venturia inaequalis by five antagonistic fungi

1997 ◽  
Vol 75 (4) ◽  
pp. 632-639 ◽  
Author(s):  
A. Ouimet ◽  
O. Carisse ◽  
P. Neumann
Keyword(s):  
Venturia Inaequalis ◽  
Apple Scab ◽  
Carbon Sources ◽  
Continuous Light ◽  
Continuous Darkness ◽  
Cold Temperatures ◽  
Factors Affecting ◽  
Nutritional Conditions ◽  
Aureobasidium Sp

The environmental (temperature, pH, and light) and nutritional (carbon sources) factors that affect the inhibition of mycelial growth of Venturia inaequalis by five fungi (Aureobasidium sp. (P26A), unidentified fungus (P28A), Phoma sp. (P59A), Phoma sp. (P66A), and Ophiostoma sp. (P164A)) were evaluated. Cold temperatures slightly reduced the inhibition of V. inaequalis by Phoma sp. (P66A). A neutral pH increased the inhibition by the unidentified isolates and by a Phoma sp. (P66A). Continuous darkness enhanced the inhibition of the pathogen by the isolate Aureobasidium sp., and continuous light favored the inhibition by the Phoma sp. (P66A). The conidial germination of V. inaequalis was significantly reduced by all the isolates, and the inhibition was stronger closer to the fungal colony. Ophiostoma sp. inhibited 100% of the pathogen's growth regardless of temperature, pH, and light regime. Only the presence of peptone in the medium diminished the inhibition by 8%. Since Ophiostoma sp. strongly inhibited V. inaequalis (92–100% inhibition) and was not influenced by environmental and nutritional conditions, this fungal isolate could be considered in the development of a biocontrol agent against the apple scab pathogen. Key words: apple scab, biological control, environment, nutrition.

Control of nitrogen assimilation in Stichococcus bacillaris by growth conditions

1987 ◽  
Vol 65 (3) ◽  
pp. 432-437 ◽  
Author(s):  
Iftikhar Ahmad ◽  
Johan A. Hellebust
Keyword(s):  
Glutamine Synthetase ◽  
Nitrogen Assimilation ◽  
Continuous Light ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Dark Cycle ◽  
Continuous Darkness ◽  
Cell Carbon ◽  
Stichococcus Bacillaris ◽  
Mixotrophic Conditions

Stichococcus bacillaris Naeg. (Chlorophyceae) grown on a 12 h light: 12 h dark cycle divides synchronously under photoautotrophic conditions and essentially nonsynchronously under mixotrophic conditions. Photoassimilation of carbon under photoautotrophic conditions was followed by a decline in cell carbon content during the dark period, whereas under mixotrophic conditions cell carbon increased throughout the light–dark cycle. The rates of nitrogen assimilation by cultures grown on either nitrate or ammonium declined sharply during the dark, and these declines were most pronounced under photoautotrophic conditions. Photoautotrophic cells synthesized glutamine synthetase and NADPH – glutamate dehydrogenase (GDH) exclusively in the light, whereas in mixotrophic cells about 20% of the total synthesis of these enzymes during one light–dark cycle occurred in the dark. NADH–GDH was synthesized almost continuously over the entire light–dark cycle. In the dark, both under photoautotrophic and mixotrophic conditions, the alga contained more than 50% of glutamine synthetase in an inactive form, which was reactivated in vitro in the presence of mercaptoethanol and in vivo after returning the cultures to the light. The thermal stability of glutamine synthetase activity was less in light-harvested cells than in dark-harvested cells. The inactivation of glutamine synthetase did not occur in cultures growing either heterotrophically in continuous darkness or photoautotrophically in continuous light. This enzyme appears to be under thiol control only in cells grown under alternating light–dark conditions, irrespective of whether this light regime results in synchronous cell division or not.

The Daily Rhythm of Activity of the Cockroach, Blatta Orientalis L

1940 ◽  
Vol 17 (3) ◽  
pp. 267-277 ◽  
Author(s):  
D. L. GUNN
Keyword(s):  
Activity Rhythm ◽  
Continuous Light ◽  
Locomotory Activity ◽  
Continuous Darkness ◽  
Daily Cycle ◽  
Blatta Orientalis ◽  
Physical Stimuli ◽  
Inactive Phase ◽  
Set Up ◽  
Main Activity

1. In an aktograph at 25.5°C., at upwards of 75% relative humidity and with food present, the average locomotory activity of the cockroach per day does not depend on whether there is continuous light for weeks, or continuous darkness, or a daily alternation of light and darkness. 2. When temperature and humidity do not vary during the day and other factors are kept as constant as possible, the cockroach's activity can be largely concentrated into any desired half of the day, simply by suitably adjusting the time of onset of the half-day's darkness. A rhythm can thus be set up, so that the main activity occurs at the same hours each day. 3. This activity rhythm persists for some days in continuous light or continuous darkness, but eventually activity becomes much more evenly spread over the whole day, leaving only a slight residual rhythm which is unrelated to the previous conspicuous one. A new conspicuous rhythm can then be started at once by alternation of light and darkness. 4. There are indications that animal responses to physical stimuli may depend to a considerable extent on whether the animal is in the active or the inactive phase of its daily cycle. A method is suggested for making it possible to study the nocturnal phase during the daytime.

Light-induced suppression of the rat circadian system

1995 ◽  
Vol 268 (5) ◽  
pp. R1111-R1116 ◽  
Author(s):  
P. Depres-Brummer ◽  
F. Levi ◽  
G. Metzger ◽  
Y. Touitou
Keyword(s):  
Locomotor Activity ◽  
Body Temperature ◽  
Circadian Rhythms ◽  
Prolonged Exposure ◽  
Light Exposure ◽  
Continuous Light ◽  
Circadian System ◽  
Short Exposure ◽  
Complete Suppression ◽  
Continuous Darkness

In a constant environment, circadian rhythms persist with slightly altered period lengths. Results of studies with continuous light exposure are less clear, because of short exposure durations and single-variable monitoring. This study sought to characterize properties of the oscillator(s) controlling the rat's circadian system by monitoring both body temperature and locomotor activity. We observed that prolonged exposure of male Sprague-Dawley rats to continuous light (LL) systematically induced complete suppression of body temperature and locomotor activity circadian rhythms and their replacement by ultradian rhythms. This was preceded by a transient loss of coupling between both functions. Continuous darkness (DD) restored circadian synchronization of temperature and activity circadian rhythms within 1 wk. The absence of circadian rhythms in LL coincided with a mean sixfold decrease in plasma melatonin and a marked dampening but no abolition of its circadian rhythmicity. Restoration of temperature and activity circadian rhythms in DD was associated with normalization of melatonin rhythm. These results demonstrated a transient internal desynchronization of two simultaneously monitored functions in the rat and suggested the existence of two or more circadian oscillators. Such a hypothesis was further strengthened by the observation of a circadian rhythm in melatonin, despite complete suppression of body temperature and locomotor activity rhythms. This rat model should be useful for investigating the physiology of the circadian timing system as well as to identify agents and schedules having specific pharmacological actions on this system.

THE REDUCTION OF AROMATIC NITRO COMPOUNDS MAGNESIUM AND METHYL ALCOHOL

1953 ◽  
Vol 31 (11) ◽  
pp. 1064-1077 ◽  
Author(s):  
Karl F. Keirstead
Keyword(s):  
Methyl Alcohol ◽  
Relative Proportion ◽  
Complex Mixture ◽  
Nitro Compounds ◽  
Factors Affecting ◽  
Azoxy Compounds ◽  
Aromatic Nitro Compounds ◽  
Aromatic Nitro

A study has been made of the reduction of substituted nitro compounds by magnesium in methyl alcohol. Some nitro compounds smoothly reduce to the corresponding azoxy compounds, while others yield a complex mixture of azo, azoxy, and other compounds. An investigation has been made of the various factors affecting the velocity of the reaction and the relative proportion of the products. An attempt is made to clarify the various reactions taking place.

scholarly journals Bivalves rapidly repair shells damaged by fatigue and bolster strength

2021 ◽  
Vol 224 (19) ◽  
Author(s):  
R. L. Crane ◽  
J. L. Diaz Reyes ◽  
M. W. Denny
Keyword(s):  
Shell Growth ◽  
Fatigue Loading ◽  
Epifluorescence Microscopy ◽  
Mytilus Californianus ◽  
Environmental Threats ◽  
Rapid Repair ◽  
Shell Deposition ◽  
Repetitive Loading ◽  
Plastic Changes ◽  
Mussel Shells

ABSTRACT Hard external armors have to defend against a lifetime of threats yet are traditionally understood by their ability to withstand a single attack. Survival of bivalve mollusks thus can depend on the ability to repair shell damage between encounters. We studied the capacity for repair in the intertidal mussel Mytilus californianus by compressing live mussels for 15 cycles at ∼79% of their predicted strength (critically fracturing 46% of shells), then allowing the survivors 0, 1, 2 or 4 weeks to repair. Immediately after fatigue loading, mussel shells were 20% weaker than control shells that had not experienced repetitive loading. However, mussels restored full shell strength within 1 week, and after 4 weeks shells that had experienced greater fatiguing forces were stronger than those repetitively loaded at lower forces. Microscopy supported the hypothesis that crack propagation is a mechanism of fatigue-caused weakening. However, the mechanism of repair was only partially explained, as epifluorescence microscopy of calcein staining for shell deposition showed that only half of the mussels that experienced repetitive loading had initiated direct repair via shell growth around fractures. Our findings document repair weeks to months faster than demonstrated in other mollusks. This rapid repair may be important for the mussels’ success contending with predatory and environmental threats in the harsh environment of wave-swept rocky coasts, allowing them to address non-critical but weakening damage and to initiate plastic changes to shell strength. We highlight the significant insight gained by studying biological armors not as static structures but, instead, as dynamic systems that accumulate, repair and respond to damage.

Core temperature in the female rat: effect of pinealectomy or altered lighting

1976 ◽  
Vol 231 (2) ◽  
pp. 355-360 ◽  
Author(s):  
F Spencer ◽  
HW Shirer ◽  
JM Yochim
Keyword(s):  
Core Temperature ◽  
Continuous Light ◽  
Mature Female ◽  
Female Rats ◽  
Female Rat ◽  
Light Phase ◽  
Continuous Darkness ◽  
Temperature Rhythm ◽  
Two Component ◽  
Lighting Regimen

Radiotelemetry of core temperature in unrestrained, mature female rats revealed the existence of a 24-h rhythm that was bimodal. The principal peak occurred during the night under control conditions of 14 h light and 10 h darkness, and a less pronounced, secondary peak occurred 3-4 h after the onset of the light phase. Shifts in the phase of the photoperiod or alteration of the proportion of light per day revealed that the temperature rhythm was entrained by light, but that the two component peaks were governed by different aspects of the lighting regimen. Exposure of rats to continuous darkness, continuous light, or to a 20-h photoperiod revealed that the primary rhythm was endogenous, entrained by circadian photoperiods only, whereas the secondary rhythm was exogenous, requiring a circadian light/dark rhythm. A relationship between mean core temperature and ttion pressure, end-systolic L was constant, despite variations in filling and therefore independent of initial L and delta L; moreover, the L to which the ventricle shortened was determined by the course of the systolic force L-relation. Thus, irrespective of loading, delta L occurs within the confines of the contractile state-depdendent isovolumic force-L relation and where the latter is equivalent to the end-systolic force-length relation.

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