摘要:

β‐galactosidase has been chosen as an indicator of glycoprotein metabolism in Acetabularia, an unicellular and uninucleate green alga. This catabolic enzyme was quantified by fluorecence spectrometry. It was found at all developmental stages, but the activity levels differed, peaking at the end of the growth phase, at the time of cap morphogenesis initiation, β‐galactosidase activity is also subjected to periodic modulation, displaying a bimodal rhythm with a prominent peak at 16 h. The distribution of the enzyme was examined by cytochemistry, using a substrate analogue (X‐gal). It is present both in the cytoplasm and in the cell wall. No apico‐basal gradient was detectable. The physiological role of glycoproteins was assessed with tunicamycin, an inhibitor of N‐linked glycoprotein synthesis. Two pulses of 3 or 4 h of inhibitor (10 μg ml‐1) always inhibited growth, but more severely during the light period. One pulse may inhibit growth during the light period and stimulate it during the dark one; it may also have little effect, in both periods. Cap formation is inhibited between time 0 and 7. During the dark or subjective dark period, it is often stimulated or not affected. The same results were obtained in constant light. Cap formation is also inhibited in anucleate algae treated during the light period.

ISSN:0022-1945    

DOI:10.1080/09291019209360184

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0022-1945    

DOI:10.1080/09291019209360189

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Long‐term records of the number of food approaches per 30 min were obtained from rabbits fedad libitum. In the initial experiments 13 rabbits were alternately kept free‐running in constant illumination at 150–200 lux, or entrained to sawtooth regimes in which illumination at the same level was abruptly switched on at 24‐hr intervals and decreased in a linear way to 0 lux over 24 hours, or was modulated in the opposite direction. Between the two entrained states there were specific differences in shape of the food intake pattern and in its phase relation with the entraining photic transition, suggesting that the rabbit's food intake pattern is determined by two weakly coupled oscillators with widely different sensitivities and types of response to the two transitions within 24‐hr LD alternations. This was confirmed by the results of further experiments, performed with 10 of the original rabbits. These were now exposed to 24‐hr photic schedules that were systematically varied in such a way that each of the two transitions occurred over many months at a fixed time of day or night, whereas during periods of many weeks the opposite transition was either left out (exposure to sawtooth illumination) or occurred after one out of five intervals (exposure to standard LD alterations). Analysis of the steady state patterns and of the transients in between pointed to the presence of two oscillators that could nearly independently be entrained by the light ON‐ and light OFF transitions of photoperiods with a length from 10 hr up to 19 hr. Although LD regimes with such photoperiods induced markedly different food intake patterns, the total number of food approaches per 24 hr was kept remarkably constant.

ISSN:0022-1945    

DOI:10.1080/09291019209360185

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The profiles of thyroxine (T4) and triiodothyronine (T3) in serum were monitored at 4 h intervals over a 24 h cycle in nine months of the year in females of the freshwater catfish.Clarias batrachusby means of radioimmunoassay. The results exhibited significant seasonal changes of the daily cycles in the titres of T4and T3. Interestingly, unlike earlier reports, T4and T3showed two peaks in the serum; one in the photophase and the other in the scotophase of the 24 h cycle in all of the studied months. There were significant variations in their peak timings and magnitudes over the year.

ISSN:0022-1945    

DOI:10.1080/09291019209360186

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

During the progressive phase of the seasonal breeding cycle four groups of male buntings were treated with (i) Normal saline (control), (ii) Luteinizing hormone (LH), (iii) L‐Dihydroxyphenylalanine (L‐DOPA, a dopamine precursor) given 8 hr after 5‐Hydroxytryptophan (5‐HTP, serotonin) (8‐hr relationship) and (iv) LH and these neurotransmitter precursor drugs with the same temporal relationship (LH + 8 hr). The results indicate that at the end of the study, while the controls as well as the LH treated birds exhibited full breeding condition (although its degree of development was higher in the latter), the testes of birds of the “8‐hr group”; showed complete atrophy. But, the birds receiving both treatments (LH + 8 hr) were not different from the controls. The body weight responses of the birds followed the same pattern as those of testes weight.

ISSN:0022-1945    

DOI:10.1080/09291019209360187

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The locomotor activity of adult femaleLycosa tarentulahas been registered in cages provided with photoelectrical cells. This activity has been studied a) under natural LD cycle and b) under constant conditions (DD, LL). A circadian rhythm was found under natural LD; an infradian rhythm under LL; and an ultradian rhythm under DD. Our results show that the natural LD cycle is an important Zeitgeber for locomotor activity rhythm.

ISSN:0022-1945    

DOI:10.1080/09291019209360188

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0022-1945    

DOI:10.1080/09291019209360183

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor