Complete censuses and samples

"Complete decennial censuses are needed for small areas and other domains. Sample surveys yield diverse and timely data. Censuses can also be combined with samples, and sometimes with data from registers, for diverse estimates that are detailed over both space and time, and hence are timely for small domains. Methods of 'postcensal estimates' for small domains are described. We note uses of censuses for improving samples and of samples for improving censuses, and propose a method for cumulating data from 'rolling' (or rotating) periodic (weekly, monthly or quarterly) samples specifically designed to cover the population in detail over designed spans (annual and quinquennial)."

An evaluation of total parenteral nutrition using Vamin and Aminosyn as protein base in critically ill preterm infants

A total of 75 preterm infants with gestation less than 32 wk received total parenteral nutrition (TPN) using Vamin and Aminosyn as protein base lasting more than 20 days. They were monitored for signs of liver dysfunction, cholestatic jaundice, and TPN-induced metabolic bone disease (osteopenia of prematurity). It was observed that severity of TPN-induced cholestasis depends on the duration of TPN and quantity of protein infused. When used as a protein base, Vamin seemed to be superior to Aminosyn. TPN-induced metabolic bone disease was strongly correlated to the duration of TPN. We suggest close monitoring of critically ill preterm infants on TPN for quantity of protein infusate, liver dysfunction, cholestatic jaundice, and TPN-induced metabolic bone disease. Intravenous protein intake should be limited to less than 2.5 g/kg/day in preterm infants with gestation less than 32 wk.

A comparative study of the membrane structure in different types of muscle fibers in the frog

The muscle membrane of slow and fast fibers in cruralis and iliofibularis muscles and of intermediate fibers in submaxillaris muscle of the frog is studied in freeze-fracture replicas. A comparison of membrane folds, number, size and distribution of caveolae and of intramembrane particles (IMP) is given. In slow muscle fibers, the membrane folds are systematically present at the level of the I zone with a transversal continuity, whereas in fast and intermediate types the membrane folds are small and are randomly distributed. In slow muscle the caveolae are more numerous at the I zone than in the part corresponding to the center of the sarcomere. In fast muscle, small groups of caveolae form linear patterns, and in intermediate fibers the distribution is random. The number of caveolae in slow muscle fibers is two times more than in fast and intermediate fibers. The mean area of caveolae opening is largest in fast and smallest in slow muscle fibers. The number of IMP is significantly different in the three types of fibers, being highest in slow and lowest in intermediate fibers. The different pattern of folds in slow fibers may correspond to the different contractile properties of this fiber type. The presence of double the number of caveolae in slow fibers correlated to the less elaborate T system in this fiber type shows the possibility that slow fibers may be the result of an arrest during development for the performance of a different function. The difference in IMP density in the three muscle fiber types may be interpreted as the difference in their electrical properties.

Structure and distribution of neuromuscular junctions on slow muscle fibers in the frog

Neuromuscular junctions on slow fibers in frog cruralis muscle have been examined with light and electron microscopy. The slow fiber bundle of this muscle is approximately half slow fibers and half fast twitch fibers. Each slow fiber has two-five clusters of nerve terminals in its central region. In contrast, fast fibers in the same bundle have single anastomosing neuromuscular junctions. The average length of terminal clusters on slow fibers is half that of the terminals on fast fibers. Less cholinesterase activity is associated with nerve terminals on slow muscle fibers. The two types of muscle fiber were identified in freeze-fracture replicas by characteristic patterns of the sarcolemmal caveolae and square arrays. Presynaptic membranes of terminals on fast fibers have long, paired double rows of intramembrane particles which lie along the sides of ridges aligned above each fold in the muscle. Ridges are less prominent or absent in terminals on slow fibers and the associated membrane particles are more often in single rows. The lengths of the particle rows also tend to be shorter and rows tend to branch and to lie at various orientations with respect to the longitudinal axis of the terminal. The average length of the particle rows per unit length of nerve terminal on slow fiber terminals is half that of particle rows on fast fiber terminals. It is concluded that the total length as well as the concentration of these active zone specializations is less at terminals on slow fibers. The lack of parallel orientation of the presynaptic active zones at slow fiber terminals corresponds to a lack of postsynaptic folds. Postsynaptic specializations seen in thin sections through slow fibers are either on flat expanses of sarcolemma or on low sarcolemmal bulges. Patches of large intramembrane particles, similar to those on fast fibers, mark regions of postsynaptic specialization in freeze-fracture replicas of slow fibers.

The presynaptic active zones in three different types of fibres in frog muscle

Presynaptic active zones were studied in slow, fast and intermediate types of frog muscle fibres in freeze-fracture replicas. In fast fibres, the double rows of paired particles are present on active zone ridges perperdicular to the longitudinal axis of the nerve whereas in slow fibres active zone ridges are rudimentary or absent and double rows of particles occur in all directions, mostly paired, sometimes single. In the intermediate type of muscle fibres both types of active zone deployment coexist on a single muscle fibre.

Innervation and membrane specialization at neuromuscular junctions in submaxillaris muscle of the frog

The submaxillaris muscle of the frog after zinc iodide-osmium staining reveals the presence of polyneural innervation. Cholinesterase staining shows that the longer terminals have postsynaptic folds whereas the smaller terminals (up to 5 micron) lack them. Thin-section electron microscopy shows that muscle fibers with or without an M line have terminals with and without postsynaptic folds. The terminals with postsynaptic folds have presynaptic membrane outpocketings above folds. These outpocketings are rudimentary or absent in the terminals without postsynaptic folds. In longer junctions, the P face of the presynaptic membrane has double rows of paired particles on active zone ridges perpendicular to the axis of the muscle. In smaller junctions active zone ridges are rudimentary or absent and double rows of particles form various patterns. Postsynaptic active zones in longer junctions consist of clusters of particles leaving gaps in between, whereas in the smaller junctions they lack gaps. The polyneural innervation and different deployment of membrane particles at neuromuscluar junctions could be a factor responsible for different physiological properties of this muscle.

Ultrastructural changes in human endometrium at different phases of the menstrual cycle and their functional significance

A review of the ultrastructure of normal human endometrium at different phases of the cycle is presented. The structural changes are correlated to the functional implications in the light of the recent knowledge on the functioning of cell organelles. Relatively undifferentiated cells of the beginning of the menstrual phase become functionally matured, proliferate and later degenerate. The appearance of the nucleolar channel system during the secretory phase coincides with the rise of progesterone level and facilitates the nucleocytoplasmic exchange. The secretion of the endometrial glands consists of glycogen, glycoproteins, lipids and mucopolysaccharides. Large autophagic vacuoles (giant lysosomes) digest various cell components at the end of the cycle. All the lamina functionalis of the endometrium is not shed, a part of it is regressed by focal death (autophagic vacuoles) and by total death (apoptosis) of individual cells.

Ultrastructural alterations in human endometrium caused by intrauterine contraceptive devices

Biopsies of endometrium from women using intrauterine contraceptive devices (IUDs) were examined by electron microscopy to elucidate the possible cause of IUD-associated uterine hemorrhage. The findings reveal the presence of degenerated, shrunken cells in the endometrial glands of IUD users. These cells, termed pyknotic or apoptotic, are more prevalent in tissue from women with complaints of excessive bleeding than in cases without such complaints. The pyknotic cells often show discontinuities of the plasma membrane at their luminal pole, from which cell contents stream into the lumen. Sometimes erythrocytes are also observed in the lumen. A second alteration in the ultrastructure of the endometrium is an abnormal increase in microfilaments in the epithelial cells. These two changes, a large number of pyknotic cells on the one hand and increase in microfilaments on the other, are correlated with excessive bleeding but they do not explain in simple terms of outflow of erythrocytes. Probably some inflammatory mechanism is involved. The increased number of microfilaments might be helping the movement of fluid from healthy to pyknotic cells.

Some ultrastructural observations on the denervated skeletal muscle of frog

The frog skeletal muscle resists atrophy for a long time after denervation. If, however, the entry of the nerve is prevented for more than 3.5 months, small muscle portions, sometimes containing nucleus, are sequestered from the parent muscle fibre. The basal lamina does not dissociate from these detached muscle portions.

Satellite cells in denervated muscles

It is known that, in a denervated striated muscle, the satellite cells multiply by mitotic division. A liaison between these satellite cells and the Schwann cell in front of the post-synaptic membrane in denervated frog muscle has been observed. It is probable that such cell connections help in the subsistence of the Schwann cell in a denervated muscle.

A comparative study of physiological and structural changes at the myoneural junction in two species of frog after transection of the motor nerve

Structural and functional behaviour of motor end-plates after transection of the motor nerve has been studied in two species of frog: Rana esculenta and Rana temporaria. The physiological results show that in both species there is a transient cessation of spontaneous activity followed by a resumption of miniature end-plate potentials (min. e.p.p.s.) after denervation. The characteristics of these potentials (frequency, distribution of amplitudes, time-course) are similar in the two species. However, some differences have been observed: Firstly, the period of silence lasts for 2--4 days in the case of Rana temporaria whereas it is prolonged to about 15 days in Rana esculenta. Secondly, the resumption of min. e.p.p.s. is gradual and after the 10th day of denervation remains constant in Rana temporaria. It is inconstant independent of the period of denervation in Rana esculenta. The morphological results show that the Schwann cell is constantly in contact with the post-synaptic membrane after about 6 days of denervation in both species. It is suggested that either the Schwann cell is capable of functioning for a limited period of time in Rana esculenta or is activated to produce min. e.p.p.s. only in certain cases.

Synaptic and non-synaptic acetylcholinesterase activity in the electroplaque of Mormyrid fishes

Electron microscopical study of AChE localization in the Mormyrid electric organ shows intense enzymatic activity in the synaptic region of the pedicle and a clearly recognizable enzymatic activity on the non-synaptic surface of the pedicle and on the anterior non-innervated face of the electroplaque.