The epithelium of the excretory duct of the human submandibular gland: a transmission and scanning electron microscopic study

The duct of the human submandibular gland (Wharton) is lined by a pseudostratified epithelium consisting of principal and basal cells. Scattered among them are a few goblet and ciliated cells. The principal cells are columnar in shape with many mitochondria, numerous dense bodies and a central nucleus with some indentations. Their apical cytoplasm shows a number of clear vesicles, some of which are reactive to silver and are extruded by exocytosis into the lumen. Other vesicles, which are unreactive, may represent the products of the absorption process. A mechanism of apocrine secretion is also observed in the principal cells. Thus, with regard to its functions, the duct of the human submandibular gland modifies the composition of saliva by adding a secretory component to it. This latter material is derived from the goblet cells but chiefly from merocrine (exocytosis) and apocrine secretion of principal cells.

Effect of dopamine on human gastric and pancreatic secretion

It has previously been shown that dopamine stimulates pancreatic exocine secretion and inhibits acid secretion in the dog. In this study, the authors have investigated the effect of dopamine on human gastric and pancreatic secretions. In 6 subjects, dopamine produced a dose-dependent inhibition of pentagastrin-stimulated acid secretion, an effect that was suppressed when the subjects received haloperidol. In 6 other subjects, dopamine infusion did not modify basal pancreatic secretion, and dopamine inhibited pancreatic enzyme secretion during secretin-cholecystokinin infusion. Dopamine also caused a rise in plasma glucagon and insulin. The effects on pancreatic enzyme secretion and plasma glucagon were not antagonized by haloperidol. The results suggest that dopamine is inhibitory for human gastric secretion. The authors did not observe a stimulatory effect of dopamine on human pancreatic exocrine secretion as has been observed in dogs.

Dual inotropic effect of harmaline on the rat heart atrial muscle

The effect of harmaline (HME) was analyzed in rat atrial strips superfused in vitro. A dual inotropic action was found: the positive component was due to a transient catechol-mediated enhancement of the velocity of development of tension (dT/dt) and to a prolongation of the duration of the rising phase of the contraction (TPT). The negative component was due to a depression of dT/dt, which overcame the persistent TPT-prolonging effect of HME, and it was abolished by rising the [K]0. It is concluded that: (1) the positive inotropic effect of HME depends on its actions on the dT/dt and TPT; (2) the enhancement of dT/dt is due to an adrenergic mechanism, which stimulates the Ca2+-dependent slowly activated current (Is); (3) a negative inotropic effect becomes evident whenever the dT/dt is depressed by the drug, regardless of the persistence of the TPT-prolonging effect; (4) the depression of the dT/dt is not due to an inhibition of Is.

Interphase chromosome arrangement in Anopheles atroparvus

The arrangement of chromosomes in interphase nuclei of Anopheles atroparvus has been inferred from an analysis of: 1. The early stages of mitosis as seen following Quinacrine staining, and 2. The reversible effects on the chromatin pattern obtained following the treatment of living cells with various NaCl solutions, and the following conclusions have been reached: (a) The chromatin is connected to the nuclear membrane, (b) Homologous chromosomes show close side-by-side somatic pairing, (c) The long arms of the sex chromosomes form a fluorescent peripheral body, (d) The autosomes are strongly reflexed at the centromeres, (e) The autosomal centromeric regions are polarized towards the peripheral body, (f) The telomeric regions of all the autosomes are closely apposed.--A ring-shaped pattern of interphase chromatin is constantly and reversibly induced by NaCl 0.15 to 0.18 M solutions.--These relationships indicate a peripheral arrangement of the interphase somatic complement.--The distribution of the chromosomes in polytene nuclei and at the beginning of meiosis resembles that suggested above for somatic interphase cells. This distribution may apply more widely in the Diptera.

Homologous bands on the long arms of the X and Y chromosomes of Anopheles atroparvus

The long arms of the X and Y chromosomes of the mosquito Anopheles atroparvus (2n equals 6) are equal in length, synchronous in their late DNA replication and have homologous G AND Q bands. This indicates that differentiation of the two sex chromosomes was the consequence of a single deletion of an autosome to give the Y chromosome, not followed by the acquisition of differential heterochromatic blocks.

The effect of harmaline on force of contraction of the rat isolated atrium

In rat isolated right atria, beating spontaneously at 30 degrees C, harmaline 8.3 times 10-5 M slowed atrial rate and enhanced force of contraction. The velocity of development of tension (dT/dt) increased and time to peak tension was lengthened. Electrical drive of otherwise quiescent left atria showed that (1) within the range of change of rate induced by harmaline the reduction of frequency of stimulation increased dT/dt and peak tension developed, and (2) at a constant rate of stimulation harmaline produced a prolongation of time to peak tension and an enhancement of peak tension. We concluded that two mechanisms are responsible for the inotropic action of harmaline on rat atrium: (1) an increase in dT/dt due to the lengthening of the interval between beats; (2) a direct action of harmaline on the processes responsible for atrial contraction, which determines a lengthening of time to peak tension.