S.L. Bellavia

Modification of the β-adrenergic sensitivity of rat submandibular gland by constant light

Rats exposed for 2, 5, 10, 20, 35 and 50 days to constant light (CL) showed beta-adrenergic desensitization of the submandibular gland as indicated by dose-response curves to 1.5, 2.0, 3.0, 10.0, 30.0 and 50.0 micrograms/kg isoproterenol. The phenomenon, evident with 1.5, 2.0 and 50.0 micrograms/kg after 2 days at CL, was more intense as time of exposure increased to reach values of about 50% those for controls after 20 days. After 35 and 50 days, desensitization showed some reversion, but the secretory responses were still lower than for controls maintained under a typical photoperiod. In the groups of rats exposed to CL for 20 days, gland wet and dry weights were higher (10%) than those of controls. These changes probably indicate an adaptation of the sympathetic control of salivary secretion induced by environmental illumination.

α-Amylase circadian rhythm of young rat parotid gland: An endogenous rhythm with maternal coordination

The circadian rhythm of alpha-amylase, E.C. 3.2.1.1. alpha-1,4-glucan-4-glucanohydrolase) in the parotid glands of 25-day-old rats were studied under different experimental designs (fasting, reversed photoperiod, constant lighting conditions and treatment with reserpine and alpha-methyl-p-tyrosine). The rhythm of fasted rats did not change. There were modifications in the rhythm of rats submitted to a reversed photoperiod or treated with reserpine or alpha-methyl-p-tyrosine. The rhythm was present, with changes in the acrophase, in parotids of rats kept during their gestation and postnatal life in constant light or dark. Results suggest that the circadian rhythm of alpha-amylase in parotid gland of young rats is endogenous, synchronized by the photoperiod, and with maternal coordination.

Effects of continuous light on rat parotid gland structure and reactivity.

SummaryThe effects of continuous light on ultrastructural organization and sympathetic secretory responses of the rat parotid gland are reported.After 50 days of continuous light exposure, the fine structure of the parotid gland exhibited features of enhanced secretory activity as judged by the striking development of rough endoplasmic reticulum and Golgi complexes, the depletion of secretory granules and the increased turnover of secretory cells. The secretory responses of parotid gland to isoproterenol revealed that continuous light induced a 30% increase in amylase release. This secretory hyperactivity appears to be related to a postsynaptic supersensitivity of sympathetic fibers of the autonomic nervous system.

Sex difference in the rate of postnatal development of amylase activity in the rat parotid gland

Abstract Changes in α-amylase (α-1-4-glucan-4-glucanohydrolase, EC 3.2.1.1.) activity after birth were in 3 stages. Significant differences were found between the sexes in the development of α-amylase activity. During the first stage, amylase activity increased more rapidly in females, whilst, in the second stage, the increase was greater in males.

Effect of sympathetic denervation of the pineal gland on maternal co-ordination of the circadian rhythm of α-amylase in parotid gland from young rats

Twenty-five-day-old rats maintained in constant darkness since birth and born from mothers kept in the dark since the 14th day of pregnancy showed a circadian rhythm of alpha-amylase content in parotid glands, which may be explained by a mechanism of maternal co-ordination. Rats in the same conditions, except that their mothers had been submitted to bilateral excision of the superior cervical ganglia 30 days before mating, did not show diurnal variations of alpha-amylase activity in the parotid glands. When ganglionectomized mothers were treated with a daily dose of melatonin (1 mg/kg) from the 14th day of gestation up to the 10th day of lactation, their litters showed significant diurnal variations of amylase in the parotid glands, suggesting a role of the maternal pineal gland in the maternal-fetal and/or maternal-neonatal transfer of photoperiodic information.

Effect of sexual steroids upon ontogeny of alpha-amylase of rat parotid gland

SummaryThe effect of gonadectomy (at the 10th day of life) and treatment with sexual steroids (during the first month) upon development of alpha-amylase activity in rat parotid gland has been studied.Alpha-amylase specific activity of parotid glands from 20-day-old orchidectomized rats and from 25-day-old ovariectomized animals was significantly higher than that of intact male and female rats of the same age respectively. Spayed males treated with testosterone (10 μg/day on the 13th, 15th, and 17th day) and ovariectomized rats treated with oestradiol (2.5 μg/day from the 16th to the 22nd day) showed values of enzymic activity similar to those of normal animals.Results indicate that oestradiol and testosterone have an inhibitory effect upon the increase of alpha-amylase activity in parotid gland during a very defined period of development.

Localization of Immunoglobulin A in Electrophoretic Patterns of Proteins from Human Parotid Saliva

Proteins from human parotid saliva were separated by use of a standardized technique of electrophoresis on polyacrylamide gel. Several fractions were eluted from the gel and studied by immunochemical methods (immunodiffusion, hemagglutination, and immunoelectrophoresis). The presence of IgA was demonstrated in the three slowest bands of the pattern.

Ontogeny of alpha-amylase circadian rhythms in rat parotid gland

The content of alpha-amylase (alpha-1,4-glucan-4-glucanohydrolase, EC 3.2.1.1.) and total soluble proteins of parotid glands (from rats exposed to a photoperiod of 14 hr light: 10 hr dark), have been determined every 2 or 3 hr over 24 hr periods in 15, 25 and 90-day-old rats. In 35-, 45- and 72-day-old rats, determinations were performed only at 0100 and 1400 hr. The alpha-amylase and total soluble protein contents from 90-day-old rats show a circadian variation, with a maximum value at 2200 hr and a minimum at 1400 hr. Parotids from 15- and 25-day-old rats also show a circadian rhythm. The minimum value is recorded at 0100 hr and the maximum at 1400 hr. At day 35 and after, there is an inversion of the amylase rhythm. In immature rats, it appears that alpha-amylase and soluble protein are under the influence of another synchronizer, whose timing is independent of that imposed by mastication of solid food.

Ontogenesis of alpha-amylase in rat parotid gland during postnatal development

SummaryChanges in α-amylase (α-1,4-glucan-4-glucanohydrolase, EC 3.2.1.1) of parotid gland were investigated during postnatal development of the rat. Modifications in amylase activity after birth allow the distinction of three stages which can be correlated with the morphologic development of the parotid gland. Significant sexual differences in the evolution of α-amylase activity were found. During the first stage (from birth to the 20th day) there is a higher increase in females, while males have a more pronounced increment in the second stage (from the 20th to the 30th day). By means of gel electrophoresis of parotid extracts, four molecular forms of amylase can be separated. The slowest migrating band (Form 1) is not detected at the initial stage.

Prenatal and Neonatal Diazepam Administration Synchronizes Testicular Malate Dehydrogenase Circadian Rhythms in Young Rats

Rat or hamster pups exposed to constant light or darkness since birth exhibit many circadian rhythms synchronized with those of the mother. During early development, a number of cues derived from the maternal circadian system synchronize the fetal and neonatal circadian clock. Maternal pineal sympathetic denervation during early pregnancy disrupts maternal synchronization of parotid α-amylase and testicular malate dehydrogenase circadian rhythms in rat pups. Maternal pineal sympathetic denervation was used to study potential agents able to synchronize the fetal or neonatal circadian clock. Melatonin injection to denervated pregnant mothers prevents the pineal sympathetic denervation effect on those circadian rhythms. We now studied the synchronizing effect of a benzodiazepine compound, diazepam. This GABAA agonist synchronized testicular malate dehydrogenase (MDH) activity of pups when it was injected to sympathetic denervated pregnant dams (a daily dose at 07:00 or 19:00 h from the 14 th to the 20 th day of gestation) or orally administered to the pups (a daily dose at 19:00 h from the 10 th to 24 th day of life). Co-injection of diazepam and GABAA antagonist, flumazenil, blocked the synchronizing effect of diazepam. The results demonstrate that diazepam has a synchronizing effect on the development of the circadian clock in rats and suggest that modulation of maternal GABAA could participate in mammalian maternal synchronization.