Narrow tubule

The plasmodesmata may be aggregated in primary pit fields or in the pit membranes between pit pahs. The plasmodesmata appear as narrow canals (2 pm) lined by a plasma membrane and are traversed by a des-motubule, a tubule of endoplasmic reticulum. The plasmodemata are dynamic altering their dimensions and are functionally diverse. For example, whereas some transport endogenous plant transcription factors, others transport numerous proteins from companion cells to enucleated sieve elements. 

Affer incubafion wifh collagenase, various changes were seen. In incipienf erosive lesions formed in HAc af pH 5.0, fhree differently stained layers were observed (fig. 9A). When fhe secfions were taken from slices demineralized affer fixafion, the layer on the bottom of the lesion (1) could not be distinguished from the underlying mineralized dentin and was apparently unaffected. It was covered by a narrow and faintly stained layer of irregular thickness (2). Tubules surrounded by more intensely stained material were present in this area. The top layer (3) consisted of intensely stained material and had a uniform appearance, with a few tubules still discernible. Erosive lesions formed in HAc at pH 5.5 resembled those formed in HAc at pH 5.0, except that the top layer was absent. The depth of the lesions could be measured accurately only in buffer-treated lesions and was approximately 90 pm (pH 5.0) and 50 pm (pH 5.5). 

Aquaporin-1, shown here, occurs in the proximal tubule and in Henle s loop. It contains eight transmembrane helices with different lengths and orientations. The yellow-colored residues form a narrowing that only H2O molecules can overcome. 

After oral administration it is well absorbed and is not protein bound. It not metabolised and is excreted mainly in urine and it inhibits the reabsorption of sodium in renal tubules. It has narrow margin of safety. 

The fibrous network was identified as being composed of two elaborated membrane systems, the system of transverse tubules which are narrow invaginations of the plasma membrane and the sarcoplasmic reticulum which constitute an intracellular complex network of membranous tubules and cistemae (Fig. la)17. The transverse tubules have been identified as the structures along which the action potential is conducted inwards. 

The mammalian epididymis is a highly coiled duct where sperm undergo maturation and are stored prior to ejaculation. The epididymis is comprised of a head (caput), a body (corpus), and a tail (cauda), which can be defined by their relative location, tissue characteristics, and cell types. Within a connective tissue sheath, the epididymis is a complex of tubules lined with columnar epithelial cells attached to a basement membrane. Epithelial cell height decreases and luminal diameter increases from the initial segment to the cauda of the epididymis. There are several distinct epithelial cell types found in the mammalian epididymis, including the principal, narrow, basal, clear, and halo cells. The principal cells... 

The wave effects concerning the organization of a controlled tubulization in a resonance regime in multiphase systems, three-dimensional current and deagglomeration of associates, lead to obtaining dispersions with narrower particle size distribution and, consequently, more homogeneous films with an increased level of physicomechanical properties. 

The sarcoplasmic reticulum membranes are the main constituents of muscle s intracellular membranes, consisting of the transverse tubular membrane system and the longitudinally oriented sarcoplasmic reticulum proper [7,8], The transverse tubules are narrow invaginations of the plasma membrane along which the electrical excitation spreads inwards [9j. They must be considered as differentiated plasma-lemma [10-12], In contrast, the sarcoplasmic reticulum membranes constitute a closed intracellular membrane system not connected with the external fluid [13,14]. It consists of different structural elements, (1) the large cistemae which are opposed to the transverse tubules or the plasmalemma, and (2) the so-called free sarcoplasmic... 

If the airborne particles are small enough, disease-causing microbes gain access to the lower stages of the lungs where bronchial tubules become progressively narrow. Infection is more likely to ensue when the agent particles... 

Hardening and narrowing of the arteries of the kidneys, a condition usually associate with high blood pressure and arteriosclerosis. Nephrosclerosis causes degeneration of the renal tubules, and fibrosis of the glomeruli, the points where filtration occurs. Its incidence increases with age but it often produces no outward symptoms. It may, however, account for the decrease in kidney reserve noted in the elderly. During its late stages some sodium and protein restrictions may be necessary. 

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