Development of Bombesin-Like and Histamine-Like Innervation in the Bullfrog (Rana catesbeiana) Central Nervous System
Bibliographic record
Abstract
Amphibians rely exclusively on behavioral thermoregulation to maintain body temperature within species- and developmental stage-specific critical limits. Several members of the bombesin family of peptides and histamine are included in a class of neurochemicals that have potent thermoregulatory effects in ectothermic and endothermic vertebrate species and may be involved in behavioral thermoregulation in amphibians. Because amphibians respond to environmental temperature cues differently in larval versus adult animals, we used immunocytochemistry to study developmental changes in bombesin-like (BN) and histamine-like (HA) innervation in the bullfrog brain and spinal cord. Neurons and fibers that were BN-immunoreactive and HA-immunoreactive were present in the earliest stage tadpoles examined (Gosner stage 29); BN-immunoreactive perikarya were found only in the preoptic area, posterior thalamic nucleus and in the rostroventral tegmentum of the mesencephalon. In the preoptic area, dramatic changes were observed in the number and staining intensity of BN-ir somata; neuronal labelling was greatest in tadpoles undergoing tail resorption (i.e. metamorphic climax) and was nearly absent in adults. Neurons immunoreactive to BN in the ventral mesencephalon also were developmental stage-dependent; limb-bud growth stage tadpoles had the largest numbers of labelled neurons, whereas in the adults, labelled cells were rarely visible in this area. The highest density of fibers was in the medial septum, lateral amygdala, and the optic tectum. Fewer fibers were observed within the dorsal and ventral hypothalamus, the pineal gland, and all the thalamic nuclei. Perikarya immunoreactive to HA were localized in the dorsal infundibular nucleus of the hypothalamus. Immunoreactivity was present in all developmental stages examined, and the numbers of labelled cells increased throughout metamorphosis to a maximum in adult brains. Fibers were found in the medial septum, medial amygdala, preoptic area, thalamus, pineal gland, hypothalamus and optic tectum. These results show that BN- and HA-immunoreactivities are established early in larval development, but their phenotypes are differentially expressed during larval and adult growth stages. This pattern suggests that reorganization of BN-like and HA-like neural circuitry may occur during metamorphosis and may be involved in the reported developmental changes in amphibian thermoregulation. In addition, BN-like peptides and HA may modulate other related mechanisms of amphibian thermoregulation and behaviour, such as thermal acclimation, circadian shifts in temperature selection and feeding. To what extent they are involved in amphibian thermoregulation remains to be investigated.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".