Phillip G. Sokolove

The chi square periodogram: Its utility for analysis of circadian rhythms☆

Abstract It is proposed that chi-square statistic be employed in constructing periodograms for the analysis of hourly time series data obtained in studies of circadian rhythmicity. We show that even for relatively short (10 day) time series, the integral-valued chi-square periodogram can distinguish circadian-periodic from random series at a level of significance of about 0·01. In addition, we describe the effects of serial correlation and examine the resolving power of the method for two periodic components in the circadian range. We suggest how the method can be most profitably employed in the analysis of event-recorder data for detection of rhythmicity in the range 14 to 34 h., and for the estimation of period to ±0·2 h.

Lactic acid-sensitive receptors on the antennae of the mosquito,Aedes aegypti

Summary1.A pair of chemoreceptor neurons sensitive to lactic acid (LA) was identified in the grooved-peg (A3) sensilla on the antennae of the mosquito,Aedes aegypti.2.One chemoreceptor responded to LA with an increase in spike frequency, whereas the other chemoreceptor exhibited a decrease in spike frequency when presented with LA.3.CO2, either alone or in combination with LA, elicited no change in spike frequency of either LA-sensitive neuron, indicating that the behavioral synergism of CO2 and LA occurs centrally and not at the primary receptor level.4.Water vapor induced such a weak excitatory response in both LA-sensitive neurons that their involvement in the detection of water vapor is questioned.5.The insect repellent, DEET, inhibited both LA-sensitive neurons. DEET plus LA was additive in the LA-inhibited cell, whereas the LA response of the LA-excited cell was attenuated by DEET.6.The reaction spectra of the LA-sensitive neurons were determined using pure compounds (Table 1).7.The importance of LA in the host-finding behavior of the mosquito is discussed.

Chronic Clorgyline Treatment of Syrian Hamsters: An Analysis of Effects on the Circadian Pacemaker

Clorgyline, a type A monoamine oxidase inhibitor with antidepressant properties when administered to depressed patients, is often associated with disturbances of the human sleep-wake cycle. In order to assess its effects on the mammalian circadian system, this drug was administered chronically to Syrian hamsters. It was found to affect the hamster circadian system in four specific ways. Clorgyline increased the intrinsic period of wheel-running ac tivity, altered the phase response curve to brief light pulses, altered the educed waveform of running activity in animals maintained in light-dark cycles or constant darkness, and in creased the activity-rest ratio in animals maintained in constant darkness. Our data support the interpretation that clorgyline exhibits direct or indirect input to the circadian pacemaker and alters the processing of photic information to the pacemaker.

Reproductive maturation in the slug,Limax maximus, and the effects of artificial photoperiod

SummaryMaturation of the reproductive tract ofLimax maximus was studied in a natural population using a reproductive organ-to-body weight index. Male-phase maturation, denoted by enlargement of the hermaphrodite gland (gonad), took place mainly in June and July. Female-phase maturation, signaled by growth of the albumen gland, occurred primarily in September. When slugs were subjected to artificial photoperiods consisting of long (LD 16∶8) or short (LD 8∶16) days, female-phase maturation was not found to be significantly affected by photoperiod (Fig. 4). In contrast, male-phase maturation appeared to be induced by a short-day to long-day transition (Fig. 7). Implications of this finding for normal seasonal maturation are discussed and a maturation sequence involving both photoperiodic and endocrine control mechanisms is suggested.

Brain-gonad axis and photoperiodically-stimulated sexual maturation in the slug,Limax maximus

SummaryPhysiological and endocrine mechanisms mediating long-day (LD 16∶8) triggered sexual maturation were studied in the terrestrial slug,Limax maximus. Our findings were: (1) Maturation was induced in immature slugs seeing only short days (LD 8∶16) after implantation of whole brains from maturing donors, but no development was found in sham-operated control slugs or in animals receiving implants of muscle from mature donors (Table 1). (2) Removal of the optic tentacles did not block maturation in LD 16∶8 or promote maturation in LD 8∶16 (Fig. 1). (3) Gonadectomy (castration) abolished penis development in 9 of 11 slugs exposed to LD 16∶8 for periods of up to 31 weeks (Table 2). The results are consistent with a model forLimax reproductive tract development in which the perception of long days by extraocular receptors results in the secretion of a “maturation hormone” by the brain followed by the production of a separate “male-phase sex hormone” by the developing gonad.

Galactogen synthesis-stimulating factor in the slug, Limax maximus: Cellular localization and partial purification

Galactogen synthesis in the albumen gland of the slug Limax maximus is under direct endocrine control [J. van Minnen, J. Wijdenes, and P. G. Sokolove (1983) Gen. Comp. Endocrinol. 49, 307-314]. The present results show that dorsal body cells (DBC) present throughout the connective tissue around the circumesophageal brain are the major cellular source of a galactogen synthesis-stimulating factor (GAL-SF). The amount of GAL-SF varies during sexual maturation of L. maximus (a protandrous hermaphrodite): it is low when animals are immature and reaches a peak in the late female phase when the animals prepare to lay eggs. The morphology of DBC also changes during maturation. DBC are small and release little secretory product in immature and early male-phase animals; release is higher and DBC are larger in late female-phase animals. Gel filtration of homogenates of cerebral ganglia on Sephadex G75 yields one peak of GAL-SF activity with an estimated Mr of 4000-7000 Da. Subsequent anion exchange chromatography showed that GAL-SF could be eluted with a linear NaCl gradient; GAL-SF was found in fractions with a NaCl concentration between 0.04 and 0.07 M.

Endocrine control of galactogen synthesis in the albumen gland of the slug, Limax maximus

An in vitro method for culturing Limax maximus albumen glands is described in which the biosynthetic activity of the slug albumen gland was monitored by measuring the incorporation of [14C]glucose into galactogen. Homogenates of the central nervous system were shown to cause a 3.5- to 12-fold increase in galactogen synthesis in albumen gland explants as compared to controls. The major sources of the galactogen-synthesis stimulating factor (Gal-SF) were found to be the cerebral ganglia and their surrounding connective tissue. Gal-SF was demonstrated to be peptidase sensitive and heat labile suggesting that it is probably a polypeptide. Autoradiographs of semithin araldite sections supported the incorporation data: in albumen gland explants cultured with cerebral ganglion homogenate considerably more label was found over secretory granules than in control-cultured explants. The possible cellular source of Gal-SF is discussed in relation to its possible origin in other investigated pulmonates.

The Use of E-Mail and In-Class Writing to Facilitate Student–Instructor Interaction in Large-Enrollment Traditional and Active Learning Classes

Student–instructor communication was examined in freshman biology classes taught either in traditional lecture style or by using a variety of student-centered, active learning approaches to engage students in the learning process (cooperative learning groups, wireless microphones, permanent name tags, in-class and out-of-class writing). In both classes students were encouraged to send questions, comments, and suggestions to the instructor via e-mail. In the active learning class, students also wrote in-class notes to the instructor. All messages could be classified as either content-related or procedural. More content-related messages were received in the active learning class than in the traditional class. Also, the percentage of students who sent content-related messages was much higher in the active learning class than in the traditional class. Finally, content-related messages from students in the active learning class were generally more thoughtful and insightful than those from students in the traditional class.

Slug reproductive maturation hormone: In vivo evidence for long-day stimulation of secretion from brains and cerebral ganglia

SummarySlugs (Limax maximus) that would normally remain reproductively immature in short-day light cycles (LD 8∶16) were employed as hosts for brain explants. Reproductive tract development was induced in hosts receiving whole brains from donors exposed to long days (LD 16∶8), but no development occurred in hosts receiving short-day brains (Fig. 1 and Table 1). Development equivalent to that induced by whole, long-day brains was also induced by implanting only cerebral ganglia from long-day donors (Table 2). Implantation of subesophageal complexes from long-day donors failed to stimulate reproductive organ growth but significantly inhibited somatic growth (Table 2). The results indicate that long-day photoperiods stimulate the release of a maturation-inducing factor from cells located in the cerebral ganglia of theLimax brain. It also appears that a growth-inhibiting factor is produced by the subesophageal ganglia.

Male gonadotrophic factor in brain and blood of photoperiodically stimulated slugs

A pulmonate male gonadotrophic factor (MGF) has been described that is released from cerebral ganglia of male-phase slugs (Limax maximus). This factor produces, directly or indirectly, an increase in spermatogonial proliferation as determined by in vivo incorporation of [3H]thymidine into gonadal DNA. In the present investigation MGF activity was demonstrated in saline homogenates of male-phase cerebral ganglia by injecting homogenates into immature slugs for 5 consecutive days and assaying gonadal [3H]thymidine incorporation on Day 7. Dose-response data indicate that daily administration of as little as 0.1 brain equivalent can produce a significant stimulation in incorporation. Comparison of brain homogenates from immature (short-day) and male-phase (long-day) animals has shown that male-phase cerebral ganglia contain substantially more MGF activity than immature ganglia. Similar injection experiments using slug blood plasma showed that activity is present in male-phase blood but not in the blood of short-day immatures. MGF activity in long-day brain homogenates and blood plasma was found to be associated with a molecular weight fraction of 50 to 100 kDa obtained by ultrafiltration. Activity could be reduced or destroyed by treatment with trypsin or by heating. The present findings suggest that MGF is a proteinaceous factor of substantial size. It appears that both the synthesis and the secretion of MFG are stimulated in slugs that are in their male developmental phase as a result of prior exposure to long-day photoperiods.