Changes In Functional Structure Research Articles

Stability of the Peritoneal Membrane in Long-Term Peritoneal Dialysis Patients

One of main challenges of peritoneal dialysis (PD) is the functional and vital long-term stability of the peritoneal membrane. Few longitudinal and controlled studies on peritoneal function have been published, and the results are somewhat contradictory. We have performed a longitudinal study with 90 patients. The overall analysis has shown that creatinine mass transfer coefficient (MTC) significantly increases and ultrafiltration (UF) capacity decreases over time. Nevertheless, urea MTC remained unaltered and MTC ratios significantly decreased after the third year. Subsequently, we examined the clinical outcomes and identified 19 patients who required peritoneal resting periods for Type I UF failure and 71 patients who did not require such a procedure. The latter patients did not show any significant functional change over time, whereas the former 19 patients showed an increase of peritoneal creatinine transport and a loss of UF capacity. These data corroborate changes in long-term peritoneal function in approximately 20% of PD patients. These changes consist of an increase in effective exchange area, peritoneal permeability, or both, accompanied by signs suggestive of mesothelial regenerative capacity loss. Infectious peritoneal injuries, especially appearing during late PD periods, are deleterious to the peritoneum. The remainder of the functional-structural changes are related to the effects of currently used dialysate. Early diagnosis, preemptive, and therapeutic measures should permit better management of long-term PD patients. The particular response to these injuries has individual characteristics that when addressed permit PD to be used long-term.

Effects of the interaction of porcine pancreatic lipase with AOT/isooctane reverse micelles on enzyme structure and function follow predictable patterns

Aerosol OT/isooctane reverse micelles were used to investigate the dependence of the lipolytic activity of porcine pancreatic lipase on surfactant concentration. Kinetic constants for the lipolytic reaction were measured in parallel with structural studies using protein fluorescence and circular dichroism (CD) spectroscopy. K m and k cat values decreased with increasing surfactant concentration at constant water to surfactant ratio ( w o = 11.85 from 25 to 100 mM AOT. These data suggested an association of the lipase with the micellar membrane and an uncompetitive inhibition of lipase activity by AOT. Structure prediction based on far-UV CD spectral data demonstrated structural reorganization of porcine pancreatic lipase upon incorporation into reverse micelles that was characterized by a large increase in β-sheet, a decrease in α-helix, and slight increases in the random and β-turn elements of structure. Other spectral changes of the lipase upon incorporation into reverse micelles included a blue shift in the fluorescence emission maximum from 342 to 335 nm and a 2.2-fold increase in the fluorescence intensity. These structure-function changes seem to be characteristic for the incorporation of lipases in AOT/isooctane reverse micelles.

Participation of auxin and abscisic acid in the regulation of seasonal variations in cambial activity and xylogenesis

The current notion that hormonal level and cell response are clearly correlated has often been challenged recently. During the period of cambial activity, auxin content seems to control the intensity of mitosis and some features of the resulting wood, but not the duration of the active period itself. During cambial rest, the indole-3-acetic acid (IAA) level often remains high in the cambium, but the cell sensitivity to auxin is low. The decrease of auxin transport in autumn is sometimes interpreted as a major qualitative change affecting the pattern of transport, and sometimes as a secondary change occurring later than rest onset. The causes of the seasonal variation of cambial response remain unknown. A hypothesis is proposed that accounts for the structural-functional changes occurring in cambial cells during the onset of dormancy. Abscisic acid (ABA) may reduce wood production and xylem cell enlargement in late summer. An important amount of ABA may be present in the cambial zone in autumn after drought stress and in spring in the young growing shoot. Changes in ABA level do not appear to be clearly correlated with the different steps of cambial rest and activity. Beyond the role of ABA as a stress mediator, its participation in the annual regulation of cambial activity remains unclear. Its distribution in the most alkaline compartments may account for the particularities of its seasonal activity. The involvement of IAA and ABA in cambial growth is discussed within the scope of a possible annual alternation of two different metabolisms in the cambial cell.

Contracture and cell damage in calcium paradox is not caused by lipid peroxidation.

The role of oxygen radicals and lipid peroxidation in calcium-paradox injury in isolated perfused rat hearts was studied by examining the effects of mannitol and (or) allopurinol on this phenomenon. Myocardial changes due to calcium paradox were characterized by contractile failure, a rise in resting tension, and cell damage. These changes were also accompanied by increased lipid peroxidation, as indicated by an increase in malondialdehyde content. Mannitol (an effective quencher of hydroxyl radicals) treatment resulted in a dose-dependent decrease in lipid peroxidation but did not affect other changes due to calcium paradox. Allopurinol (an inhibitor of xanthine oxidase) neither affected lipid peroxidation nor modified any of the structure-function changes due to calcium paradox. These data demonstrate the occurrence of lipid peroxidation which, however, may not be involved in the observed structure-function changes due to calcium paradox. It is also suggested that in this experimental model, xanthine oxidase may not be the inducer of oxygen radicals or of lipid peroxidation.

Evidence for widespread atresia in the hypophysectomized estrogen-treated rat.

The question considered in this study concerns to what extent the ovaries of the immature hypophysectomized diethylestilbestrol-treated rat are populated by atretic follicles. Histological studies of ovaries on postoperative days 4-7 reveal the presence of numerous follicles showing signs of ill health. The granulosa cells constituting these follicles are heterogeneous and exist in three distinct zones. The cells in zone 1 are affixed to the basal lamina and form a tightly packed sheet of cuboidal epithelium one to two cells thick. The cells constituting zone 2 are located just medial to zone 1 and appear as a mass of loosely aggregated cells which show intense necrosis. Zone 3 is composed of the prospective cumulus-oocyte complex which appears completely normal. Results of histochemical studies show heterogeneity in the granulosa cells with respect to the presence and location of markers specific for atresia. In atretic follicles, the granulosa cells populating zones 1 and 2 contain lipid droplets and esterase activity, but are negative for the lysosomal enzyme acid phosphatase. The exact reverse is true for zone 3, where the cumulus express intense acid phosphatase activity but are negative for lipid and esterase activities. The granulosa cells in healthy follicles are totally negative for these histochemical markers. As a healthy preantral follicle grows, there is a dramatic increase in the mitotic index of the granulosa cells; however, in all atretic follicles, granulosa cell division is decreased by more than 90%. Further experiments using monoclonal antibodies as probes confirm the presence of atretic follicles and demonstrate that the structure-function changes in zones 1 and 2 are associated with striking changes in the antigenic properties of the granulosa cells. Morphometric studies indicate there are a total of 235 +/- 29 preantral follicles/ovary in the hypophysectomized diethylstilbestrol-treated rat. On postoperative day 4, 37 +/- 1.2% of the preantral follicles are atretic; this number increases linearly with time posthypophysectomy, reaching nearly 50% on postoperative day 7. Examination of follicles at different stages of development reveals that atresia is rare in the very early stages, e.g. follicles less than 200 microns in diameter; however, in the population of larger preantral follicles (those 200-400 microns in diameter), atresia is common, with nearly 80% being atretic on postoperative day 7. Collectively, these findings provide convincing evidence of widespread atresia in the ovaries of the hypophysectomized diethylstilbestrol-treated rat.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of bulk structure of amino silane primer on the strength and durability of aluminum/epoxy joints

AbstractThe strength and durability in wet environment of aluminum/epoxy/aluminum joints are investigated as a function of structural changes of γ aminopropyltriethoxy silane (γ‐APS) primer at the interface. Both dry and wet strengths exhibit strong dependencies on both the thickness and the extent of drying of γ‐APS prior to joint formation. Generally, dry strength decreases with increasing thickness of γ‐APS primer, and increases with dehydration of γ‐APS at any given thickness. Strength retention of the joints after exposure to water at 55°C also improves dramatically when the adsorbed γ‐APS is extensively dried. These results are analogous to earlier observations with α‐Al2O3/polyethylene joint system. In aluminum joints, porous oxide substrate facilitates the mechanical interlocking mechanism, and its interplay with both the thickness and the extent of cure of γ‐APS is analyzed by characterizing the fractured surfaces using scanning electron microscopy (SEM) electron spectroscopy for chemical analysis (ESCA).

Theory and model of the human global analysis of visual structure; Part II: The space-time and visual value segment

For pt.I see ibid., vol.SMC-12, no.6, p.805-17 (1982). A theory is presented that describes the human visual structure analysis as an effort aimed at segment formation and consequent segment structure identification. Segments occur and are processed at different levels of globality. Structure is latent in the photic signal, ready to be extracted and manipulated by eye behavior and retinal processing. This latent structure may be objectively studied by assessing the spatial relations between positions with the same photic signal power. Subjective segmentation is thought to occur as a result of adjustments of the hypothesized object-to-retina transfer function, spatiotemporal fixation parameters, and corticofugal control of neural processing in the ganglion layer of the retina. Experimental results support the hypotheses concerning adjustments of visuomotor programming as a function of structural changes of the stimuli.

Giardiasis: Clinical Spectrum and Functional-Structural Abnormalities of the Small Intestinal Mucosa

We studied 17 adult and 11 pediatric patients with giardiasis in order to examine the clinical spectrum and the functional-structural changes of the small intestinal mucosa. The most common clinical manifestations were diarrhea, weight loss, abdominal cramps, and, in children, failure to thrive. Giardiasis was frequently associated with hypogammaglobulinemia (HGG) and intestinal nodular lymphoid hyperplasia (47% and 41% of adults, respectively). Malabsorption of D-xylose and vitamin B12 occurred in 55% and 60% of patients, respectively, steatorrhea in 64%, and hypocarotinemia and low serum folate in 36%. No or only slight mucosal abnormalities were present in pretreatment jejunal biopsies of 75% of those adults on whom biopsies were performed, whereas 25% (all with HGG) had marked inflammation and changes of the villus-crypt architecture. Marked structural changes were seen in 43% of subjects with HGG. Estimates of brush border enzymes showed a significant reduction in lactase, sucrose, and leucyl-naphthylamidase specific activity in about 80% of patients assayed, whereas maltase, isomaltase, and alkaline phosphatase were not affected. Five patients were studied prospectively and absorption tests and jejunal mucosal biopsies were repeated after treatment with metronidazole or quinacrine. Resolution of symptoms with restoration of the morphologic and functional abnormalities of the small intestinal mucosa occurred after treatment in all but 1 patient. These observations indicate that Giardia cause brush border damage, which, is usually reversible with eradication of the parasite. Other factors, alone or in combination with Giardia, may be responsible for the cell damage beyond brush border injury found in some patients.

Effects of High and Low Erucic Acid Rapeseed Oils on Energy Metabolism and Mitochondrial Function of the Chick

Duplicate experiments were conducted to compare energy utilization, growth, cardiac mitochondrial oxidative phosphoryl,tion, and mitochondrial membrane fatty acid composition of chicks fed diets containing 20 parts of high erucic acid rapeseed oil (HER), low erucic acid rapeseed oil (LER) or sunflower seed oil (SFO) for 24 days. Chicks fed diets containing HER deposited less fat and utilized energy less efficiently (kcal gained/kcal consumed) than chicks fed diets containing either LER or SFO. Energetic efficiency and fat deposition of chicks pair-fed diets containing LER were significantly lower than for chicks fed diets containing SFO. Cardiac mitochondria isolated from chicks fed diets containing either HER or LER for 24 days had significantly reduced ADP/O ratios and reduced rates of ATP synthesis utilizing pyruvate and malate as the respiratory substrates when compared with mitochondria isolated from chicks fed SFO. Diet induced transitions in fatty acid composition of cardiac mitochondrial membranes were also observed. The composition of fat ingested affected the fatty acid composition of mitochondrial diphosphatidyl glycerol more than the fatty acid composition of phosphatidyl choline or phosphatidyl ethanolamine. The linoleic acid content of mitochondrial diphosphatidyl glycerol was lower and the gadoleic acid and erucic acid content higher for chicks fed diets containing rapeseed oils than for chicks fed SFO containing diets. These studies indicate that a complex dynamic mechanism exists associating dietary fat with mitochondrial structural-functional changes and energetic efficiency in the growing chick.

Quantum‐mechanical theory for transport across biological membranes

AbstractA general quantum‐mechanical description of molecular transport across biological membranes has been developed. The one‐dimensional Schrödinger equation for the motion of ions and molecules across the biological membrane has been solved using reasonable potential barriers. Two types of potential profiles for such transports have been considered: a flat barrier proposed by Hall et al. for lipids and an oscillatory potential proposed by Lauger for lipids and by us in this paper for intrinsic proteins. The general behavior of the transmission coefficient as a function of energy and the variation of the permeability as a function of structural changes in the membrane have been discussed. Finally, the importance and areas of applicability of such a theory have been pointed out.

Attitudes toward Employment and Employment Status of Mothers in Hyderabad, India

Considerable research has focused on the relations between employment of mothers and structural-functional changes within the family system. In addition, researchers have focused on the motivations of mothers to work. (Damodaran, 1958; Lafollette, 1934; Ramdev, 1960; U. S. Department of Labor, 1946; U. S. Department of Labor, 1951; Zweig, 1952). In this connection the present research effort constitutes an attempt to shed light on the relation between the employment status of mothers and selected attitudinal variables. The data presented below were selected from a larger project designed to study role conflict of employed mothers in Hyderabad, India. In all, 40 pairs of sisters (one employed as a teacher and the other performing exclusively the role of wife-mother) matched on the following variables were investigated: (1) age (difference did not exceed 5 years); (2) residence (all lived in Hyderabad); and (3) structurally intact family. Specific attitudes examined were (1) satisfaction with husband's level of income, (2) desire for material comfort, (3) educational aspirations for children, (4) desire for social contact, and (5) image of the working mother as perceived by the mother. A basic assumption of this report is that attitudes conducive to outside employment exist prior to seeking employment and are not consequences of employment.