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At least 19 recordsLinked to original sources
PubMed1978

Calorimetric studies of the structural transitions of the human erythrocyte membrane. Studies of the B and C transitions.

Differential scanning calorimetry has been used to study several structural transitions of the human erythrocyte membrane. Earlier studies have shown that one of these transitions (the A transition) is due to the thermal unfolding of spectrin on the membrane. In this paper, it is shown that two of the other transitions (B and C) exhibit a high sensitivity to a local anesthetic, benzyl alcohol. Increasing the ionic strength of the suspending medium results in a splitting of the B transition into two indepent transitions (B1 and B2). It is found that one of these (B2) is associated with titrating groups, since the midpoint for the transitions shifts by about 20 degrees C, with an apparent pK near 7.5 Extensive bilateral proteolysis by papain causes a drastic decrease in the size of all transitions except the C transition, which remains unaltered. On the other hand, treatment with phospholipase by A2 largely affects the C transition, causing its disappearance. Because of the lack of sensitivity to proteolysis and the high sensitivity to phospholipase, it appears that the C transition has a large extent of 'lipid involvement'. It might result from the melting of a small fraction of phospholipid which exists in a crystalline state under physiological conditions. Alternatively, the C transition could arise from changes in protein-lipid interactions or from lipid-dependent changes in protein-protein interactions, providing one assumes that only protease-resistant portions of membrane proteins are participating.

Calorimetry, Differential Scanning↗
PubMed1975

Transition of the R factor NR1 and Proteus mirabilis: level of drug resistance of nontransitioned and transitioned cells.

When Proteus mirabilis harboring the R factor NR1 is cultured in Penassay broth containing 100 mug of chloramphenicol (CM) per ml, there is an amplification in the number of copies of the r-determinants per cell. Under these conditions, R factors harboring multiple tandem sequences of r-determinants are formed. Autonomous poly-f-determinants consisting of multiple copies of r-determinants are also formed. This phenomenon has been referred to as the "transition". Transitioned cells have considerably higher levels of resistance to CM and streptomycin (SM), but not to tetracycline (TC), than do nontransitioned cells and grow more rapidly in medium containing either CM or SM. There is essentially no difference in growth rates between transitioned and nontransitioned cells in drug-free medium. The higher level of resistance of transitioned cells to SM has made it possible to investigate the mechanism of the transition. Using replica plating, it has been possible to isolate spontaneously occurring transitioned cells from a nontransitioned population which appear to outgrow the nontransitioned cells during growth in medium containing 100 mug of CM per ml. If transiitoned cells are subsequently cultured in drug-free medium, the cells return gradually to the nontransitioned state, which has been referred to as the "back-transition was monitored by examining the level of resisitance of the cells to SM. In both situations the cell populations were found to be heterogeneous, consisting of a mixture of nontransitioned and transitioned cells. Under the conditions of our experiments, the transition appeared to be due to the more rapid growth of a minor fraction of spontaneously occurring transitioned cells which outgrew the remainder of cells in the population. To obtain the transition, the drug resistance gene must reside on the r-determinants component of the R factor. The transition did not take place when the cells were cultured in medium containing high concentrations of TC. This indicates that the TC resistance genes reside on the resistance transfer factor component of the R factor, which is in agreement with physical studies on R factor deoxyribonucleic acid.

Bacteriological Techniques↗
PubMed2026

Transitioning to adult care for patients with IBD: the impact of a structured IBD transition program on service engagement.

BACKGROUND AND AIMS: The British Society of Gastroenterology recommend use of structured transition programs to improve control of chronic gastrointestinal disease in adolescents. We sought to determine the impact of attending a structured transition program on engagement of patients with inflammatory bowel disease (IBD) services and disease outcomes. METHODS: We performed a retrospective multicenter study of patients with IBD prior to and post-transfer to adult services. Patients were grouped into those who attended a structured transition program and those who received standard care, transferred with a referral letter. RESULTS: A total of 282 patients were included: 155 patients in our structured transition program cohort and 127 patients in the standard care cohort. Patients who took part in a structured transition program had significantly better engagement with adult IBD services with significantly lower rates of nonattendance at outpatient clinics 1-year post-transfer (12.3% vs 27.2%, P = .002) and significantly lower rates of disengagement with services (4.2% vs 13.1%, P = .015). There were no significant differences seen in rates of biologic failure, need for steroid/surgery or median fecal calprotectin levels between either group. Attending a structured transition program was the only factor that positively impacted engagement with IBD services in a multivariate analysis (OR 4.08, confidence interval 1.41-11.91, P = .01). CONCLUSION: Structured transition programs in IBD can improve engagement of patients with IBD services with significantly lower rates of disengagement with IBD services seen in our study. Large prospective studies are needed in this field to further investigate this and the impact of these programs on disease outcomes.

Humans↗
PubMed1979

Esophageal scintigraphy to quantitate esophageal transit (quantitation of esophageal transit).

None of the tests employed currently to investigate esophageal transit is quantitative. The purpose of this study was to evaluate normal subjects and patients with a variety of esophageal disorders using a scintigraphic technique to quantitate esophageal transit. After oral administration of a bolus of water labeled with 99mTc-sulfur colloid, isotopic count rates were measured over the esophagus employing a gamma-camera on line to a digital computer. Esophageal transit was expressed as the percent emptying for each of the first 15-sec after the initial swallow and for 15-sec intervals after serial swallows. Sixty-two subjects were studied, including: normal volunteers; patients with motor disorders of the esophagus such as achalasia, diffuse esophageal spasm, and scleroderma; and patients with symptomatic gastroesophageal reflux both with and without esophageal motor dysfunction on manometic testing. Esophageal transit was decreased significantly after single and multiple swallows in patients with motor disorders of the esophagus. In addition, esophageal transit was abnormal in patients with reflux disease accompanied by abnormal motor function. In contrast, esophageal transit was normal after a single swallow, but incomplete after serial swallows in patients with reflux associated with normal esophageal motor function on manometry. We conclude that esophageal scintigraphy may be used to evaluate esophageal transit.

Adult↗
PubMed1979

Mitotic index, influx and mean transit time in the hamster cheek pouch epithelium, a partially synchronized cell system. Presentation of a mathematical model based on a non-stationary probability density function for the transit time in a compartment.

Mitotic activity was followed in the epithelium of the hamster cheek pouch for about 12 hr in two experiments under different conditions of noise and light intensity. A mathematical model based on a non-stationary probability density function for the transit time through mitosis was developed, making an analysis of this partially synchronized cell system possible. The most important result of the two experiments is the indication of a non-stationary mean transit time for cells in mitosis. In the first experiment (70 dB, 103 lux), which produced high mitotic indices (maximum 2.0%), the influx changed from 0. to 0.9%/hr (mean of 7-hourly determinations: 0.4%/hr), and the mean transit time from 1.9 to 5.5 hr. In the second experiment (70 dB, 265 lux), which had a lower level of MI (maximum 1.3%), the influx changed from 0 to 1.8%/hr (mean of 13-hourly determinations: 0.4%/hr), and the mean transit time from 0.3 to 3.3 hr. It was difficult to say precisely whether the variation in influx or in mean transit time was the main factor in the increase and decrease of MI. The data could not be simulated with a stationary mean transit time. It is suggested that changes in MI due to different external circumstances are mainly the result of variation in the mean transit time.

Animals↗
PubMed1992

Transition time control analysis of a glycolytic system under different glucose concentrations. Control of transition time versus control of flux.

Control and Response Coefficients of transition time have been determined in a rat liver glycolytic system under different glucose concentrations. Results have been compared with the Flux Control and Flux Response Coefficients measured in the same conditions, showing that transition time and flux are different responses of the system, subject to different regulation and control. Control Coefficients of flux and transition time show a very different profile in each condition of glucose concentration assayed. Ratio of Flux Control coefficients of glucokinase over phosphofructokinase at 5 and 20 mM glucose concentration changes from 3.2 to 0.5, while the same ratio in the case of Transition Time Control Coefficients moves from 0.6 to 0.93. Moreover, the absolute values of Transition Time Control Coefficients in glycolytic conditions are one order of magnitude bigger than in gluconeogenic conditions. Values of Response Coefficients also show that the transition time has a bigger sensitivity to changes in glucose concentration than the flux in all conditions assayed, but particularly in glycolytic ones.

Animals↗
PubMedDate not supplied

[Phase transition studies of model and biological membranes. I. Use of hydrophobic fluorescent probes for studying phase transitions in liposomes].

Phase transition induced by temperature changes in liposomes prepared from synthetic dimyristoyl-(DML), dipalmytoyl-(DPL) and distearyl-(DSL) lecithins and also from equimolar mixture of DML and DPL and mixtures of DPL and cholesterol were studied with fluorescent probes such as 3-metoxybenzantron (MBA) and dimetylaminocholkone (DMC). The significant changes of fluorescence intensity and maximum position of MBA and DMC were found in the regions of phase transitions at 23, 42, 54 and 31c in liposomes from DML, DPL, DSL and mixture of DML and DPL, respectively. Cholesterol incorporation into liposomes from DPL led to a decrease of transition temperature and cooperativity for these liposomes. At cholesterol concentration of 20 mol. percent or more the transition disappeared completely. It is concluded that MBA and DMC can be used for the investigation of biological membranes phase transitions.

Cholesterol↗
PubMedDate not supplied

The transition to a nursing home: meeting the family's needs. Family members face their own transition when a loved one enters a nursing home.

The lack of preparation for the experience of admission to a nursing home, as represented by these family members, indicates there is a need for nursing interventions targeted to the family before the admission of a loved one to the nursing home. The program could address information and problem solving, as well as provide emotional support. The day of admission is too late to prepare for this experience. Access to families occurs before any admission to LTCFs. Nurses in acute care and home care are in a position to inform, assist, and advocate for families in this decision-making and admission process. The family members we questioned have provided some of the content for an educational preparation program that may be useful to all families. The responses also indicate that each family will have its own concerns and functional relationships that would alter specific content. Maslow's framework could aid the identification of needs and direct the specific interventions to empower the family to cope with this transition. A few guidelines have been suggested in this article to stimulate discussion about the family's transition to the nursing home. Appraisal of a family's perceptions about the use of nursing homes may alert the nurse to potential conflicts and areas of uncertainty. These assessments provide direction for family interventions that may alleviate the extent of uncertainty and conflict before the admission and serve as ongoing family-centered activity in the nursing home. The view of this experience as a family transition also supports the concept of continuity of care through nursing interventions.

Family↗
PubMed1978

Transitional steady-state investigations during aerobic-anaerobic transition of glucose utilization by Escherichia coli K-12.

Transitional steady-state investigations during changes in oxygen tension under aerobic and during aerobic-anaerobic transition conditions were carried out with the aim of finding an indicator system which separates the equilibrium from the non-equilibrium state. Of the parameters used i.e. biomass formation, CO2 production, Q02, NADH oxidase, succinate dehydrogenase, phosphofructokinase, glyceraldehyde-3 phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and 2-oxoglutarate dehydrogenase, only the three enzymes requiring NADH or NADP for their function fulfilled the requirements. Biomass production and CO2 formation were useful only during the aerobic-anaerobic transition period. In each case the response was immediate and the indicator systems demonstrated that a new steady state of oxygen was always obtained after 11 h which, at the specific growth rate used, was equivalent to at least two volume replacements of the growth vessel.

Aerobiosis↗
PubMed1992

The midblastula transition, the YSL transition and the onset of gastrulation in Fundulus.

The first signs of cell motility appear in Fundulus toward the end of cleavage, after cleavages 11 and 12. When blastomers cease cleaving, their surfaces undulate and form blebs. At first, these blebbing cell remain in place. Gradually thereafter they begin movement, with blebs and filolamellipodia serving as organs of locomotion. Non-motile cleaving blastomeres have thus differentiated into motile blastula cells. This transformation corresponds to the midblastula transition of amphibian embryos. Gastrulation in Fundulus begins with vegetalward contraction of the external yolk syncytial layer. This causes narrowing of the E-YSL and initiates the epibolic expansion of the blastoderm. Convergent movements of deep cells within the blastoderm begin toward the end of this contraction. The YSL forms as a result of invasion of the yolk cell cytoplasm by nuclei from open marginal blastomers during cleavage. These YSL nuclei then undergo five metachronous divisions. After this, they divide no more. YSL contraction begins approximately 1.5 hours after cessation of these divisions (21-22 degrees C). This cessation of nuclear divisions is preceded by a gradual decrease in rate. (1) The duration of each succeeding mitosis increases steadily and often some nuclei do not divide at mitosis V. (2) The duration of interphases between succeeding mitoses also increases, but to a much greater degree, and the longest interphase by far is the last one, I-IV, between mitoses IV and V. (3) The mitotic waves responsible for mitosis V move much more slowly than those for the first four mitoses and invariably decelerate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1977

Observations on the morphology at the transition between the peripheral and the central nervous system in the cat. II. General organization of the transitional region in S1 dorsal rootlets.

The aproximal segment of feline S1 dorsal rootlets were investigated light and electronmicroscopically. A one shaped protrusion of CNS tissue was found to extend distally into each rootlet for a distance of 100-1000 micrometer. That free segment of a rootlet which when cross sectioned revealed both CNS and PNS constituents was denoted the transitional region (TR). The TR was subdivided into an axial CNS compartment and a surrounding PNS compartment. The CNS compartment consisted of a core zone that showed the organisation of a CNS fiber tract, and of an outer astrocytic mantle zone which corresponded to the external glial limiting membrane of the brain and the spinal cord. The outer aspect of the mantle zone constituted the PNS-CNS borderline. The mantle zone was rich in astrocytes and projected a large number of thin processes--the glial fringe--distally into the endoneural space of the PNS compartment. There were large fenestration defects in the basement membrane that demarcated the endoneural space from the glial space. The mantle zone contained many large myelinoid bodies and some encapsulated small dark unclassified cells. Similar cells, some covered by a basement membrane, were at hand in the adjacent endoneural space. The myelinated nerve fibres were equipped with a node of Ranvier at their borderline passage.

Animals↗