Biomedical subjects

D Gaudino

Publications and source records attributed to D Gaudino.

7 recordsLinked to original sources

PubMed2004

Complexation of anionic polyelectrolytes with cationic liposomes: evidence of reentrant condensation and lipoplex formation.

We have studied the complexation process taking place in cationic liposomes in the presence of anionic polyelectrolytes, in the polyion concentration range from the dilute to the concentrated regime, by combining dynamic light scattering and transmission electron microscopy techniques. We employed as the cationic lipid a two-chained amphiphile (Dioleoyltrimethylammoniumpropane) and sodium polyacrylate salt as the flexible anionic polyelectrolyte. The results evidence a variety of different structures, mainly depending on the liposome-polyion charge ratio, whose peculiar dynamical and structural features are briefly described. In particular, three different polyion concentration regions are found, within which a monomodal or bimodal distribution of aggregates, with a well-defined time evolution, is present. At low polyion content, close to the isoelectric point, large aggregates are formed, deriving from the collapse of the liposomal bilayers into extended charged surfaces, where adsorbed polyions form a two-dimensional strongly correlated array and organize into a two-dimensional Wigner liquid. At high polyion content, above a critical concentration, the size distributions of the complexes are clearly bimodal and a large-component aggregate, continuously increasing with time, coexists with a population of smaller-size aggregates. At an intermediate polyion concentration, spherical, small-size vesicular structures are reformed, connected in a network by polymer chains. A brief discussion tries to summarize our results into a consistent picture.

Anions↗

PubMed2003

Time evolution of the formation of different size cationic liposome-polyelectrolyte complexes.

We report on the time evolution of the aggregation behaviour of cationic liposome-polyelectrolyte complexes studied by means of dynamic light scattering technique. Pure dioleoyltrimethilammoniumpropane (DOTAP) and mixed DOTAP-dipalmitoylphosphatidylcholine (DPPC) liposomes in polyacrylate sodium salt aqueous solutions in a wide concentration range have been investigated and the size and size distributions of the resulting aggregates evaluated from the intensity autocorrelation function of the scattered light. Under appropriate conditions, we found two discrete aggregation regimes, resulting in two different structural arrangements, whose time evolution depends on the charge ratio and the polyelectrolyte molecular weight. A first small component of average size in the 100-500 range nm coexists with a larger component, whose typical size increases with time, up to some micrometers. The cluster growth from a single liposome, 70 nm in diameter, to the formation of polymer-coated liposome aggregates has been briefly discussed in the light of steric stabilization of colloids. Moreover, it has been found that the kinetics of aggregation of the larger, time-dependent, component follows a dynamical scaling within the diffusion-limited cluster aggregation (DLCA) regime. The understanding of structures resulting from interactions between polyelectrolytes with oppositely charged liposomes may help towards formulation of "lipoplexes" (cationic lipid-DNA complexes) to use as non-viral gene carriers.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1994

Smile psychology.

Facial expression, including smiling, is an important means of universal communication and an understudied area in dentistry. Currently there is limited availability of data on smile psychology in either general or cosmetic dental literature. However, the number of cosmetic dentistry patients is increasing and many require and desire physical changes that restore or enhance facial expressions, appearances, and smiles. Cosmetic dentistry patients, particularly those presenting with dental anxiety or phobia, require a more detailed physical and psychologic assessment due to their habitual avoidance of dental care and subsequent oral health deterioration. Increasing knowledge and data facilitate the development of new intervention and treatments for anxious and phobic dental patients. These new developments strengthen the dentist-patient partnership to foster optimal dental results.

Dental Anxiety↗

PubMed1985

Effects of physical fitness on expiratory airflow in exercising asthmatic people.

Maximal expiratory flow-volume maneuvers were performed by self-trained (FIT) and sedentary (UNFIT) asthmatic subjects. Both groups had similar pre-exercise pulmonary function limitations and attained the same exercising heart rate. The FIT group, however, exercised significantly longer than the UNFIT group. Although expiratory airflow increased in both groups during exercise, the FIT group had significantly larger airflow increases than the UNFIT group and maintained them throughout the exercise. In contrast, the UNFIT group's airflow decreased prior to the end of exercise. Tidal volume (VT) expiratory curves surpassed pre-exercise maximum expiratory flow-volume (MEFV) envelopes in subjects whose tidal volume was greater than 55% of vital capacity, the majority of whom were FIT subjects. In no case, however, did the VT curve exceed the enhanced exercise MEFV curve. The increase in airflow reserve during exercise helps to explain why asthmatic athletes, despite their significantly impaired pulmonary function, can compete successfully in sports making high aerobic demands.

Adult↗

PubMed1984

Effect of mechanical loading on breathing patterns in women.

First-breath ventilatory responses to graded inspiratory elastic and resistive loads were obtained from 80 women unfamiliar with respiratory experimentation. For each load 1) responses from different subjects ranged from a weak tidal volume defense coupled with an increased breathing frequency to a strong tidal volume defense coupled with a decreased frequency; 2) strong tidal volume defenders employed longer inspirations than did weak tidal volume defenders; and 3) individual respiratory frequency responses were mediated by changes in inspiratory and/or expiratory timing. Thus the group response was qualitatively the same as that reported for 80 men. Quantitatively, however, mean inspiratory airflow responses of women exceeded those of men by an amount attributable to women's higher intrinsic respiratory elastance. Tidal volume responses, on the other hand, did not differ significantly, suggesting that men and women produce different neural adjustments to loads. In support of this hypothesis, analysis of respiratory timing responses revealed that 1) men actively prolonged inspiration more than women during resistive loading; and 2) women actively shortened inspiration more than men during elastic loading. These findings indicate that the load-compensating behavior exhibited by men and women is similar but not identical.

Adult↗

PubMed1983

Ventilatory adjustments during sustained mechanical loading in conscious humans.

Ventilatory responses to inspiratory elastic and resistive loads of 67 men were analyzed. During the 1st, 5th, and 10th consecutively loaded breaths 1) individual responses ranged from a rapid-shallow to a slow-deep breathing pattern; 2) strong tidal volume (VT) defenders employed longer inspirations than did weak VT defenders; and 3) individual frequency responses were mediated by changes in inspiratory and/or expiratory timing. Thus the group response was qualitatively similar on the 1st, 5th, and 10th loaded breaths. Quantitatively, however, the group's mean minute ventilation increased throughout each episode owing to progressively larger tidal volumes coupled with equal breathing frequencies. During elastic loading this amplified VT defense was achieved by stronger inspirations with no systematic changes in timing, whereas during resistive loading it was achieved both by stronger and longer inspirations. Inspiring 5% CO2 induced a degree of hypercapnia exceeding that accompanying mechanical loading and yet elicited a comparatively modest enhancement of respiratory output. These findings suggest that in conscious humans 1) repeated mechanical loading activates neural load-compensating mechanisms; 2) the range of these neural adjustments varies with both load size and type; and 3) the stimulus to initiate this behavior is largely nonchemical.

Adolescent↗

PubMed1982

Effect of upper body posture on forced inspiration and expiration.

The upper body posture naturally adopted by long distance runners was quantified, and its effects on ventilation were assessed in 14 subjects. Maximum voluntary ventilation (MVV) and flow-volume loop maneuvers were performed in three seated positions: 1) natural running posture (RUN), with back angled forward 11 degrees, neck flexed, and head extended 35 degrees forward of the spinal column; 2) back vertical with head and neck as above (NEF); and 3) head and back vertical (VERT). MVV was significantly higher in RUN compared with both NEF and VERT, as were peak inspiratory pressure (PImax) from functional residual capacity, peak expiratory flow (PEF), and peak inspiratory flow (PIF). Expiratory flow at 50% of vital capacity was significantly higher in RUN and NEF than in VERT, consistent with reported increases in flow due to tracheal stiffening. The increased PIF and PImax in RUN indicate increased inspiratory muscle tension and/or improved transduction of tension into a more negative pleural pressure. Magnetometer tracings of rib cage dimensions demonstrated greater anteroposterior stability during maximal inspiratory efforts in RUN compared with VERT. The improved inspiratory function seen in RUN may be due to more effective diaphragmatic and/or accessory muscle function. These findings demonstrate that the position naturally adopted by long distance runners favors ventilation.

Adolescent↗