Neuropeptide Y and Peptide YY Immunoreactivities in the Pancreas of Various Vertebrates

Ding, W.-G., H. Kimura, M. Fujimura and M. Fujimiya. Neuropeptide Y and peptide YY immunoreactivities in the pancreas of various vertebrates. Peptides 18(10) 1523–1529, 1997.—NPY-like immunoreactivity was observed in nerve fibers and endocrine cells in pancreas of all species examined except the eel, which showed no NPY innervation. The density of NPY-positive nerve fibers was higher in mammals than in the lower vertebrates. These nerve fibers were distributed throughout the parenchyma, and were particularly associated with the pancreatic duct and vascular walls. In addition, the density of NPY-positive endocrine cells was found to be higher in lower vertebrates than mammals; in descending order; eel = turtle = chicken > bullfrog > mouse = rat = human > guinea pig = dog. These NPY-positive cells in the eel and certain mammals tended to be localized throughout the islet region, whereas in the turtle and chicken they were mainly scattered in the exocrine region. PYY-immunoreactivity was only present in the pancreatic endocrine cells of all species studied, and localized similarly to NPY. Thus these two peptides may play endocrine or paracrine roles in the regulation of islet hormone secretion in various vertebrate species.     

Evolution of Endocrine Regulation of Gastrointestinal Function in Lower Vertebrates

The information available concerning the evolution of endocrineregulation of three gastrointestinal functions in lower vertebrates—gastricacid secretion, gallbladder contraction, and pancreatic enzymesecretion—is reviewed. The actions of hormones of thecholecystokinin/gastrin family of peptides have been the mostwidely studied and are emphasized. It is concluded that regulationof pancreatic enzyme secretion is a primitive action of cholecystokininand that the sensitivity of gallbladder muscle and gastric acid-secretingcells to these peptides evolved later, possibly in the ancestrallineage that led to the gnathostomes. The need for increaseddigestive efficiency to support the higher levels of activitymade possible by the evolution of jaws is suggested as a strongselection pressure leading to this pattern of evolution of endocrineregulation of gastrointestinal function.     

Evolution of Pineal Control of Endocrine Function in Lower Vertebrates

Pineal bodies, and other associated parietal structures, areremarkably varied among vertebrates These organs apparentlyassumed, in the primitive vertebrates, a principal role in integrationof photic information. The pineal photoreceptor cell seems tohave evolved into the secretory pinealocyte that is found inmost of the higher vertebrates. Along with the evolution ofthe photoreceptor element into the pinealocyte, there is a concomitantshift in the neural connection of the pineal organ. The pinealo-fugal,sensory innervation gives way to an autonomic, pinealo-petalmotor innervation. Thus, direct photosensitivity was supercededby indirect, optically-mediated control of the now secretorypineal gland. Even though pineal organs display such unusual plasticity anddiversity across groups, responsivenses to light remains a constantfeature. Photoperiod may modify the diurnallyrhythmic patternsof melatonin secretion across seasons and invoke appropriate"programs" which permit an animal to anticipate seasonal changes.Thus, melatonin may be a key molecule, attuned to photoperiodicity,which has been selected through evolution to effect adaptationto annual events.     

Correlation Between Iodine Intake and Thyroid Function in Subjects with Normal Thyroid Function

Excessive iodine intake is known to induce hypothyroidism in people who have underlying thyroid disorders. However, few studies have been performed on subjects with normal thyroid function without a history of autoimmune thyroid disease. We hypothesized that high iodine intake may cause a subtle change in thyroid function even in subjects with normal thyroid function. We analyzed 337 subjects (64 men and 273 women; mean age, 49 years) who showed normal levels of thyroid peroxidase antibodies (TPO-Ab) and thyroglobulin antibodies (Tg-Ab) by measuring the urinary iodine excretion, free T4 (FT4), and thyroid-stimulating hormone (TSH). The results showed urinary iodine excretion had negative correlation with FT4 (γ = −0.11, p = 0.043) and showed a positive trend with TSH (γ = 0.10, p = 0.068). We found that 61.7% of subjects had circulating TPO-Ab within normal reference range. In all subjects, TPO-Ab levels were negatively correlated with FT4 (γ = −0.17, p = 0.002) and positively with TSH (γ = 0.13, p = 0.021). In conclusion, high iodine intake can negatively affect thyroid hormone levels in subjects with normal thyroid function. Population-based study will be helpful for further clarification.     

Thyroid Function in Addison's Disease

Clinical evidence of a thyroid disorder was present in 10 out of 40 patients with Addison''s disease. Though the remaining 30 patients had no clinical evidence of thyroid disease, six (out of 15 tested) had thyroid microsomal antibodies and a considerably impaired response to thyrotrophin. These changes are interpreted as very early indications of developing thyroid failure. When circulating microsomal antibodies are found this seems to indicate the presence of established thyroid disease.     

Adaptation to Intermittent Hypoxia: Influence on the State of Endothelial Function

Human Physiology - This study involving ten apparently healthy male volunteers aged 19 to 31 years was aimed at establishing possible effects of a three-week course of normobaric intermittent...     

Environmental Influences on Thyroid Function in Teleost Fish

SYNOPSIS. A brief account of some of the influences that environmentalfactors, such as the lunar cycle, daylength and temperature,may have on thyroid activity in certain salmonids and the killifish,Fundulus heteroclitus, is presented. The rapid and immediatecharacterof temperature effects is discussed and a role for central neuroendocrinecontrolin mediating the effects of photoperiod and lunar phenomenainvolvement is suggested.     

Reporting Thyroid Function Tests in Pregnancy

While there is agreement that overt maternal hypothyroidism (serum thyroid stimulating hormone (TSH) >10 mIU/L) should be treated immediately, the evidence is mixed regarding the harm associated with subclinical hypothyroidism and the benefits of thyroxine replacement. The diagnosis of subclinical hypothyroidism rests on the recognition of an increased serum concentration of TSH which may be affected by many factors including gestational age, analytical method, the antibody status of the mother, ethnicity, iodine nutrition and even the time of day when the blood is collected. The 97.5^th percentile of TSH at the end of the first trimester is commonly used as the upper boundary of normal in early pregnancy with a default value of 2.5 mIU/L specified in a number of recent clinical guidelines. There have now been numerous papers showing that a more realistic figure is between 3.0 and 4.0 mIU/L depending on the analytical method that is used. There are suggestions that ethnicity may also have a significant effect on TSH and FT4 reference limits in pregnancy.     

The Evolution of Endocrine Systems in Vertebrates

A review of Comparative Vertebrate Endocrinology, 3rd edition, by P.J. Bentley. Cambridge: Cambridge University Press, 1998, 526 pp, $100.00, hardbound; $44.95, paperback.     

The impact of global change on terrestrial Vertebrates

Examples of the impact of human activities on Vertebrate populations abound, with famous cases of extinction. This article reviews how and why Vertebrates are affected by the various components of global change. The effect of direct exploitation, while strong, is currently superseded by changes in use of all sorts, while climate change has started having significant effects on some Vertebrate populations. The low maximum growth rate of Vertebrate populations makes them particularly sensitive to global change, while they contribute relatively modestly to major ecosystem services. One may conclude that unless they are considered as sentinels of the biological consequences of global changes, their situation will go on strongly deteriorating, in particular under the influence of interactions of different components of global change such as changes in use and climate change.     

The Timing of Timezyme Diversification in Vertebrates

All biological functions in vertebrates are synchronized with daily and seasonal changes in the environment by the time keeping hormone melatonin. Its nocturnal surge is primarily due to the rhythmic activity of the arylalkylamine N-acetyl transferase AANAT, which thus became the focus of many investigations regarding its evolution and function. Various vertebrate isoforms have been reported from cartilaginous fish to mammals but their origin has not been clearly established. Using phylogeny and synteny, we took advantage of the increasing number of available genomes in order to test whether the various rounds of vertebrate whole genome duplications were responsible for the diversification of AANAT. We highlight a gene secondary loss of the AANAT2 in the Sarcopterygii, revealing for the first time that the AAANAT1/2 duplication occurred before the divergence between Actinopterygii (bony fish) and Sarcopterygii (tetrapods, lobe-finned fish, and lungfish). We hypothesize the teleost-specific whole genome duplication (WDG) generated the appearance of the AANAT1a/1b and the AANAT2/2′paralogs, the 2′ isoform being rapidly lost in the teleost common ancestor (ray-finned fish). We also demonstrate the secondary loss of the AANAT1a in a Paracantopterygii (Atlantic cod) and of the 1b in some Ostariophysi (zebrafish and cave fish). Salmonids present an even more diverse set of AANATs that may be due to their specific WGD followed by secondary losses. We propose that vertebrate AANAT diversity resulted from 3 rounds of WGD followed by previously uncharacterized secondary losses. Extant isoforms show subfunctionalized localizations, enzyme activities and affinities that have increased with time since their emergence.