Diameter Of Microvilli Research Articles

Bioprocessed poultry by-product meals on growth, gut health and fatty acid synthesis of juvenile barramundi, Lates calcarifer (Bloch).

Poultry by-product meal (PBM) has been utilised as a substitute of fishmeal (FM) in many aquaculture species. However, little information is known regarding the use of bioprocessed PBM (BPBM) in aquaculture production. This study was undertaken to investigate whether replacing FM with BPBM improved growth performance, gut morphology and fatty acid synthesis of juvenile barramundi, Lates calcarifer. The PBM was bioprocessed by baker yeast, Saccharomyces cerevisae and Lactobacillus casei. The BPBM was used to replace FM at 75% and 100% (75BPBM and 100BPBM) contrasting against unprocessed PBM (75PBM and 100PBM) at the same levels and FM based diets as the control. Juvenile barramundi with a mean initial weight of 3.78±0.16 g were stocked at a density of 20 fish per tank. After the 42 days of study, the final weight, specific growth rate and feed conversion ratios of fish fed 75PBM and 75BPBM were not significantly different from the control. However, 100% supplementation diets of 100PBM and 100BPBM resulted in reduced performance in all growth and feed variables except total feed intake and survival. The hind gut microvillus density was significantly higher (P<0.05) in fish fed 75BPBM, whereas the microvillus diameter remained unaffected with the other experimental diets when compared to the control. A reduction in eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids of fish muscles led to a lower Σn−3/Σn−6 ratio in all dietary groups when compared to the control. The percentage of Σn-3 PUFAs decreased in 100% FM replacement diets of 100PBM and 100BPBM, while Σn−6 PUFAs increased when both bioprocessed and unprocessed PBM protein was increased in the diets. Fish fed bioprocessed diets had higher fatty acid hypocholesterolemic/hypercholesterolemic ratios (HH), indicating improved suitability for human consumption.

Effects of phosphatidylethanolamine N‐methyltransferase on phospholipid composition, microvillus formation and bile salt resistance in LLC‐PK1 cells

Bile salts are potent detergents and can disrupt cellular membranes, which causes cholestasis and hepatocellular injury. However, the mechanism for the resistance of the canalicular membrane against bile salts is not clear. Phosphatidylethanolamine (PE) is converted to phosphatidylcholine (PC) in the liver by phosphatidylethanolamine N-methyltransferase (PEMT). In this study, to investigate the effect of PEMT expression on the resistance to bile salts, we established an LLC-PK1 cell line stably expressing PEMT. By using enzymatic assays, we showed that the expression of PEMT increased the cellular PC content, lowered the PE content, but had no effect on the sphingomyelin content. Consequently, PEMT expression led to reductions in PE/PC and sphingomyelin/PC ratios. Mass spectrometry demonstrated that PEMT expression increased the levels of PC species containing longer acyl chains and almost all ether-linked PC species. PEMT expression enhanced the resistance to duramycin and lysenin, suggesting decreased ratios of PE and sphingomyelin in the apical membrane, respectively. In addition, SEM revealed that PEMT expression increased the diameter of microvilli. The expression of PEMT resulted in reduced resistance to unconjugated bile salts, but surprisingly in increased resistance to conjugated bile salts, which might be attributable to modifications of the phospholipid composition and/or structure in the apical membrane. Because most bile salts exist as conjugated forms in the bile canaliculi, PEMT may be important in the protection of hepatocytes from bile salts and in cholestatic liver injury.

Surface Ultrastructural Alterations of Bovine Oocytes after Parthenogenetic Activation

Oocyte activation is a critical component of the current animal cloning scheme. This study was designed to examine surface characteristics of bovine oocytes by scanning electron microscopy (SEM) after activation by calcium ionophore A23187 (A23187) and electric pulse combined with cycloheximide (CHX) or 6-dimethylaminopurine (6-DMAP) treatments. In vitro matured (IVM) oocytes were activated then harvested at 0 to 19 hours after the onset of treatments for SEM processing. The zona pellucida (ZP) of untreated IVM oocytes exhibited an open mesh structure. The ZP surface showed little changes after A23187 alone, but dramatically changed to a less porous surface 3 hours after combined treatments with CHX or 6-DMAP. The vitelline membrane of IVM oocytes was covered with well-developed microvilli (MV). The MV became shorter (0.83 vs. 1.35 microm, p < 0.01) 8 hours after A23187 treatment alone. The vitelline membrane was altered in all oocytes examined 3 hours after incubation with A23187 plus CHX or 6-DMAP. A 1.5-fold increase in the diameter of MV in the CHX group and a higher incidence of large cytoplasmic protrusions (more than 1 microm width) in the 6-DMAP group were observed. After removal of inhibitors, the surface morphologies of the ZP and vitelline membrane were returned nearly to those of untreated IVM oocytes in both groups. The present study clearly showed that surface characteristics of the bovine oocyte were more profoundly changed by a combination of agents for parthenogenetic stimulation, and that the ultrastructural effects were reversible.

The Effects of Mercury Exposure on the Surface Morphology of Gill Filaments in Perna perna ( Mollusca: Bivalvia)

This study investigated the possibility that changes in the surface morphology of mussel ( Perna perna) gill filaments may be used to indicate the relative toxicity of pollutants in the marine environment. Healthy, adult P. perna were collected and immersed in 2 free-flow tanks. Mercury was added to seawater as it entered tank 1 to achieve a constant level of 50 μg/l −1 over 24 days. Uncontaminated seawater was circulated over the mussels in tank 2 (control) for the same period. A 25 mm 2 area of gill filament was removed from each of the 5 specimens before and after 24 days immersion in tank 2, and after immersion for 1, 2, 4, 8, 16 and 24 days in tank 1. These were examined using a scanning electron microscope. The remaining soft tissues from each animal were analysed for mercury using an atomic absorption spectrometer. Mercury concentration increased from 0.13 (pre-immersion) to 87 μg/g after day 24. Surface morphology remained normal for all animals in tank 2 and for those exposed to Hg for up to 8 days. However, from 16 to 24 days exposure there was a gradual increase in the diameters of microvilli, a depletion of abfrontal cilia, an increase in abnormal, perhaps necrotic cells and an unusual increase in the number of cilia on the lateral surfaces. These results confirm that P. perna is an efficient bio-accumulator and suggest that their gill pathomorphology may be a useful indicator of toxicity.

Does age matter in studying the crustacean eye?

Fifty randomly selected publications dealing with aspects of crustacean vision had theirMaterials and methods sections examined. In half of the articles gleaned, only the name of the animal under study was given; the other half mentioned “adult” or “mature” animals; twelve papers provided information on size or age of the experimental animal and six gave the sex. InPetrolisthes elongatus, rhabdom microvilli not only become more regular in outline as the animal grows, but also decrease in diameter from 90.4±21.2 nm in crabs of 5.0–8.9 mm carapace length via 86.6±13 nm in crabs of 9.0–12.9 mm carapace length to 79.7±7 nm in crabs of 13.0–16.9 mm carapace length. Approximately 400 cross sectional diameters of microvilli from identical regions in four eyes of each size class were measured and provided the basis for Anova-, Levene-, andt-tests. The three size classes possess microvilli of significantly different diameters and standard deviations. Our observations show that investigators of the crustacean photoreceptor have frequently neglected to consider the size of their experimental animals, but that this practice should not be continued as the now documented changes in microvillus diameters may influence the amount of visual pigment present and, thus, the photoreceptor's sensitivity to light.

Cell Apical Surface Area in Enterocytes from Chicken Small and Large Intestine During Development

The absorptive surface of epithelial cells from chicken small and large intestine was studied at the day of hatch (1 d group) and at 2 and 6 wk after hatch. The segments considered were duodenum, jejunum, ileum, cecum (proximal, medial, and distal regions), and rectum. The length, diameter, and density of microvilli as well as cell apical diameter were measured in tip-villous enterocytes by transmission electron microscopy. The results obtained showed that during development: 1) microvillus length remained constant in duodenum and jejunum and decreased in the other segments; 2) microvillus diameter increased only in the jejunum and the rectum; 3) microvillus density increased in duodenum, ileum, distal cecum, and rectum (especially from 1 d to 2 wk) and did not change in the other segments; 4) cell apical diameter did not change; 5) apical surface area increased both in the duodenum (2nd to 6th wk) and in the jejunum (1 d to 2 wk) but did not change in the ileum. In the proximal-medial cecum and in the rectum there was a decrease in apical surface, whereas no changes were observed in distal cecum. Results indicated that microvillus length and density are the variables that best explain the changes observed in apical surface that occurred during development.

The distribution of microvilli over the villous surface of the normal human term placenta is homogenous.

The study was carried out to estimate stereologically whether regional differences exist in the distribution of microvilli between vasculo-syncytial (VSM) and non-vasculo-syncytial (non-VSM) areas of the villous surface in normal term placenta. In ten placentae a normal lobe was perfusion-fixed at a pressure of 60 mm Hg, and the intervillous space was perfused at 10 mm Hg. The tissue was routinely processed for ultrastructural examination. Stereological estimates relating to the length and diameter of microvilli, and to the villous surface amplification factor in adjacent but contrasting (VSM and non-VSM) regions, were obtained. A paired "t' test showed no significant difference in the villous surface amplification factor between the two regions (5.18 +/- 0.54 and 5.22 +/- 0.54 respectively, mean +/- s.e.m. P > 0.05). In addition, there were no significant differences between the length and diameter of microvilli in both regions (P > 0.05 in both). The results confirm that the normal term placenta has a continuous and even covering of microvilli over the syncytium.

The eye of the New Zealand freshwater crabHalicarcinus lacustris, and some eco‐physiological predictions based on eye anatomy

In specimens of Halicarcinus lacustries of 6 mm body length and width, the two compound eyes each comprise about 400 ommatidia, and anatomically resemble those of other brachyuran crabs. All ommatidia are of the apposition type with short, proximally tapering, quadripartite crystalline cones as well as a cornea (maximum thickness 18 μm) with con vexly‐curved inner surfaces. The mean distance from cornea to basement membrane is 125 μm, and interommatidial angles average 9.5°. Each ommatidium possesses a horizontally‐banded rhabdom, 35–40 μm long and 2.5 μm wide, with seven contributing retinula cells. An eighth axon can be traced to a small distally‐placed retinula cell. We conclude that the photoreceptors of H. lacustris are useful in detecting small environmental changes in brightness, as well as the plane of polarized light, but have poor spatial and temporal resolution. High densities of screening pigment granules throughout the eye, a decrease in microvillus diameter from an average of 61.1 nm distall...

An ultrastructural study on HeLa cells cultured in roller bottles forming aggregates

We will describe here the ultrastructure of HeLa cells cultured in either roller bottles for 8 days or 10 days or in Petri dishes for 7 days. Junctional complexes could be seen between adjacent cells in aggregates formed in roller bottles. The junctional complexes were serially located especially near the free surface of the cells which occupied the outer layer of the aggregates. Two elements of the junctional complex, i.e., tight junctions and intermediate junctions, were observed between adjacent cells. The density and the diameter of microvilli in the intercellular space between cells cultured in roller bottles were denser and narrower than those of microvilli on the free surface of the cells. Junctional complexes and dense microvilli formed intercellular secretory canaliculus-like structure observed in the intercellular space of certain secretory glands.

Comparison and Estimation of Absorptive Intestinal Surface Areas in Two Species of Cichlid Fish

Abstract We developed techniques for combining scanning electron microscopy with conventional measurements to estimate intestinal surface areas in blue tilapia Tilapia aurea and redbelly tilapia Tilapia zilli. These fish have natural diets that are similarly resistant to digestion. The former feeds on detritus and the latter on macrophytes. Intestinal lengths adjusted for total body length were not significantly different between the two species, but redbelly tilapia had a greater intestinal diameter. Intestinal walls of both species consisted of longitudinal folds winding through the length of the intestine. Mean fold width was greater in redbelly tilapia, but fold height did not differ between species. Scanning electron micrographs of cross sections of intestinal walls showed columnar epithelial cells topped by a brush border (i.e., microvilli) and a lamina propria underneath the epithelium in both species. Mean microvillus height was greater in blue tilapia. Microvillus diameter did not differ between ...

Effects of microflora on the dimensions of enterocyte microvilli in the rat.

The length and diameter of enterocyte microvilli at mid-villus position were measured on electron-micrographs. The duodenum, jejunum and ileum of axenic (germfree) and holoxenic (conventional) inbred rats fed the same diet have been studied. The microvilli were significantly shorter in all these intestinal regions when the microflora was present. The decrease in microvillus length (due to the presence of microflora), expressed as a percentage of the length in axenic rat, was 5% in the duodenum, 9% in the jejunum and 18% in the ileum. This was not true of microvillus diameter where only the values found for the ileum of axenic rat were significantly lower, the others not differing among themselves. In conclusion, the presence of a total microflora led to a decrease in the length of enterocyte microvilli. These results have been discussed in relation with studies on renewal and enzyme activity in the intestinal epithelium.

Morphological features of the surface of the sea urchin ( Arbacia punctulata) egg: Oolemma-cortical granule association

Scanning microscopy and transmission electron microscopy of sectioned specimens and freeze-fracture replicas revealed the presence of slightly elevated regions, approximately one-fourth to one-half the diameter of microvilli, which were situated along the surface of unfertilized Arbacia eggs. These modifications of the surface of the egg were observed in areas occupied by cortical granules and were greatly reduced in number following the cortical granule reaction. Few such modifications were present in immature and urethane-treated ova, in which cortical granules were located in regions of the egg other than the cortex. Freeze-fracture replicas of unfertilized eggs revealed a significantly higher density of intramembranous particles within the plasmalemma when compared to replicas of the membrane surrounding cortical granules. Areas characteristic of the cortical granule membrane, i.e., sparsely laden with particles, were not observed within the plasmalemma of the fertilized egg. Hence, following its fusion with the egg plasma membrane there is a dramatic reorganization in particle distribution of the membrane derived from cortical granules.

Massive diurnally modulated photoreceptor membrane turnover in crab light and dark adaptation

1. Effects of light and dark adaptation on the photoreceptor membranes of the rock crabGrapsus have been quantitatively studied using light and electron microscopy to document changes in rhabdom size and their fine structural basis. Some comparative data were also obtained for the ghost crabOcypode. Animals in the laboratory were maintained on a daily light (L)-dark (D)cycle 12L∶12D. Periods of adaptation ranged from 3–28 h (Table 1) and light adaptation was effected at one moderate intensity equal to the light period in the daily sequence. 2. Massive rapid reversible changes in rhabdom size (Fig. 1) comprising mainly diameter modulation (Figs. 2, 3) and some alteration in length, normally resulted in maximum increases in receptor organelle volume of about 20× between a thinner, shorter fully light adapted condition (2×290 μm) to the fully dark adapted state (7.9× 336 μm). 3. Rhabdom growth during dark adaptation (Table 2) was due mainly (Fig. 8) to microvillus elongation (+154%) as well as substantial increase (+117%) in the number of microvilli present in cross sections (Figs. 2, 3, 10); microvillus diameter (Figs. 4, 5, 9) also increased (+14%) but accounts for only a minor part of the overall change commensurate with observed differences in rhabdom length (+16%). Calculation shows that from fully light adapted to fully dark adapted state the area of photoreceptor membrane increased nearly 20× in a few hours. 4. Although duration of adaptation affected its amplitude, six hours of either light or darkness evoked the maximum changes documented; shorter and longer periods had less effect (Figs. 6, 7). 5. Time of day had a strong periodic influence on the amplitude of membrane adaptation produced by a given exposure to dark or light. Thus maximum dark adaptation occurred with 6 h of darkness terminating at midnight and maximum light adaptation with 6 h of light ending at noon of the diurnal light cycle (Fig. 11). 6. Direct effects of light and dark on synthesis and degradation of photoreceptor membrane must therefore be superimposed on indirect or direct cyclic neuroendocrine control presumably coupled to an entrained circadian oscillator.

Cell cycle-dependent surface changes in Chinese hamster cells grown in suspension culture

The cell surface appears to play an important part in the control of cell replication. It has been demonstrated that the cell membrane undergoes cyclic changes in appearance which bear a relation to the cell cycle phase, irrespective of close intercellular contact. The surface of Chinese hamster (CHO) cells was investigated using the scanning electron microscope (SEM). The cells were synchronized in suspension culture and were sampled at frequent intervals during the cell cycle. During mitosis, the cells showed microvilli and few blebs. In early G 1 phase, profuse microvilli were seen. In late G 1 phase, blebs appeared and persisted in great numbers. During the synthesis of DNA in the S phase, blebs were observed in the early stages and then declined in number; in G 2 phase, the blebs appeared to be larger (1–2 μm) and more sparsely distributed than in late S phase. Some of these blebs were pedunculated and, in some instances, the diameter of the pedicles approximated the diameter of microvilli. Since the reasons for these changes are not understood, our long-range goal is to correlate the observed surface changes with internal biochemical events during the cell cycle.

The Fine Structure of Plant Mitochondria

The fine structure of plant mitochondria was studied by electron microscopy in the following species: Aloe vera, Elodea canadensis, Glycine max, Yucca glauca, Zingiber officinale, Juniperus communis, Cibotium chamissoi, Psilotum triquetrum, Bryum sp., Funaria hygrometria, Marchantia polymorpha. In all these genera, without exception, the mitochondria were observed to have the same basic structure: a double membrane and a tubular or microvillous structure arising from the folds of the inner membrane. Highly organized lamellated cristae were not present in any of these mitochondria. The diameters of microvilli were measured and ranged from 280Å a to 950Å.