Testosterone changes the electric organ discharge and external morphology of the mormyrid fish, Gnathonemus petersii (Mormyriformes)

Effects of silastic and pellet methyltestosterone implants on the waveform of the electric organ discharge of the weakly electric African mormyrid, Gnathonemus petersii, were investigated. Within seven days of implantation, the duration of the discharge increased dramatically while the associated peak power frequency of the Fourier spectrum decreased in all treated fish. By day 35, hormone-treated fish exhibited up to five-fold increases in EOD duration, as well as multiple discharges and variations in the shape of the positive phase of the discharge. Testosterone treatment also changed body morphology, making immature and adult female fish resemble adult males.     

No sex difference in the waveform of the pulse type electric fish,Gnathonemus petersii (Mormyridae)

Summary A communication signal in an African freshwater electric fish, its pulse-like Electric Organ Discharge (EOD), was investigated in order to determine whether inter- or intraindividual variability of the EOD waveform provides a putative cue for communication, in addition to the electric cues already identified. In contrast to an individual's highly stereotyped EODs showing extremely low variation (fig. 1), variability between individuals was considerable (fig. 2). The dependence of an individual's EOD duration on temperature was weak with a Q₁₀ of close to 1.5. In none of four quantitative EOD waveform measures can a sexual dimorphism be discerned (table).Gnathonemus petersii very likely relies on mechanisms other than discrimination of intraspecific EOD waveforms for mate recognition.     

Development of the electric discharge in mormyrid and gymnotid fish (Marcusenius sp. and Eigenmannia virescens).

Larvae of both species start discharging at 8 days. Eigenmannia immediately produces pulses similar to those of the adult. Marcusenius however, possesses a characteristic larval discharge 20 times longer and of opposite polarity to the adult discharge which appears on Day 40.     

High frequency of human cytomegalovirus (HCMV)-specific CD8+-T cells detected in a healthy CMV-seropositive donor

Human cytomegalovirus (HCMV) persists after infection but is controlled by cellular immune responses, particularly by CD8⁺ T cells. If infected individuals are immunosuppressed, HCMV can be reactivated. Upon testing the blood of healthy donors with human lymphocyte antigen tetramers, we found one individual with about 50 % of his CD8⁺ T cells being specific for the immunodominant pp65 epitope NLVPMVATV. Over a period of 2 years the high level of HCMV-specific T cells was maintained, and no HCMV DNA could be detected. At one timepoint, however, HCMV-specific DNA was detected, while 65 % of CD8⁺ T cells were specific for HCMV. When virus was detectable, a lower percentage of HCMV-specific CD8⁺ T cells showed interferon γ (IFN-γ) production after peptide stimulation in vitro. These data suggest that HCMV reactivation may also occur in immunocompetent persons, accompanied by the presence of HCMV-specific CD8⁺ T cells which are not producing IFNγ, and therefore potentially anergic or in vivo exhausted. Received 6 March 2002; received after revision 15 April 2002; accepted 17 April 2002     

Energy metabolism,respiration frequency and O2-consumption per breathing act in 11 different sunbird species during day and night

Summary The mean metabolic rates of 11 sunbird species are in the expected range based on data from other birds. Nevertheless the difference between day and night levels is greater (58–69%) than normal. Breathing frequencies among these birds correspond more closely to the (higher) levels found in empirical data for mammals. O₂-consumption per breathing act remains nearly constant during day and night indicating that the diurnal cycle of O₂-consumption is regulated mainly by modulation of breathing frequencies, which correlate directly with gaseous metabolism.     

Photoperiodic regulation of mating behaviour in the linden bug,Pyrrhocoris apterus,is mediated by a brain inhibitory factor

Active inhibition of mating behaviour in a male insect is reported here for the first time. InPyrrhocoris apterus L. (Heteroptera), the most important inhibitory pathway runs from the pars intercerebralis (PI) of the brain and does not pass through the corpora allata. The inhibitory activity of the PI is promoted by short day conditions and suppressed by long days. As the effect of photoperiod is delayed, transfer procedures enabled us to record daily rhythms in mating behaviour during short days. While the extirpation of the PI results in a discrete phase shift of the long day rhythm, there is a much less significant phase shift after this operation during short days. Thus the PI has been shown to mediate the effect of photoperiod on both the inhibition and the rhythm of mating behaviour.     

Speed of in vitro reassociation of gonadotropin subunits in a teleost fish, the carp (Cyprinus carpio L.)]

Purified gonadotropin subunits of a teleost Fish, the Carp, reassociated in vitro, according to a second order rate reaction. The rate constant was temperature dependent. Compared to ovine LH, the Q10 was about three times less and the rate constant much greater (160 times for instance at 20 degrees C). The possible physiological significance of these differences is underlined.     

Electron diffraction of the metallic elements in the pineal organ of a freshwater fish,Mystus vittatus (Bloch.)

Summary By electron diffraction pattern the presence of metallic elements, particularly chromium-nickel, chromium phosphide, copper, aluminum-copper and zinc has been shown in the pineal organ of a freshwater teleost,M. vittatus. It is likely that their occurrence within the pineal is due to binding with the neurosecretory material fractions/ligands.The technical assistance of O.N. Srivastava and financial assistance of CSIR, India, are gratefully acknowledged.     

Electron diffraction of the metallic elements in the pineal organ of a freshwater fish, Mystus vittatus (Bloch.)

By electron diffraction pattern the presence of metallic elements, particularly chromium-nickel, chromium phosphide, copper, aluminum-copper and zinc has been shown in the pineal organ of a freshwater teleost, M. vittatus. It is likely that their occurrence within the pineal is due to binding with the neurosecretory material fractions/ligands.