PubMed Health⌕ Search

Biomedical subjects

G Careri

Publications and source records attributed to G Careri.

8 recordsLinked to original sources
PubMed1990

Proton tunneling in hydrated biological tissues near 200 K.

We measure the protonic conductivity in water clusters adsorbed on intact samples of viable biological samples (corn embryo and endosperm, Artemia cysts, and Typha pollen) below room temperature. In the low-temperature region, the conductivity increases with temperature as exp T6, in agreement with prediction by the theory of dissipative quantum tunneling. We detect the onset of this effect near 180 K, where a glass transition in the hydrated protein matrix is known to take place. Above 220 K other transitions are superimposed onto this simple behavior.

Animals↗
PubMed1989

Dielectric properties of Artemia cysts at low water contents. Evidence for a percolative transition.

Cellular cysts of the crustacean Artemia provide a useful model for studies on water-dependent mechanisms in cellular function because they can undergo reversible cycles of dehydration-rehydration. We explored their dielectric behavior over the frequency range of 10 kHz to 1 MHz, at water contents between near zero and 0.5 g H2O/g dry weight (g/g). The dc conductivity and static dielectric permittivity were evaluated from electrostatic analysis of data obtained with a three-layered capacitor. Below cyst hydrations of 0.05 g/g, negligible dielectric response was observed at all frequencies. Between 0.05 and 0.25 g/g the permittivity increased sharply then reached a near plateau up to cyst hydrations close to 0.35 g/g, above which a second abrupt increase occurred. Values for the dielectric loss (tan delta) exhibited frequency-dependent peaks over the hydration range of 0.05-0.3 g/g, followed by an abrupt increase near 0.35 g/g, an hydration at which metabolism is first initiated in this system. These hydration-dependent dielectric changes are compared with previous studies on the biology and physics of this system, and evaluated by a model involving percolative ionic (likely protonic) conduction. Percolative behavior is characterized by a sharp increase in conductivity at a critical threshold of hydration (hc) according to a power law in which the exponent, t, equals 1.65 for a three-dimensional infinite lattice. For the Artemia cyst, t = 1.64 above hc = 0.35 g/g, which is in excellent agreement with theory. These results are compared to similar studies on lysozyme which also exhibits percolative behavior connected with the onset of biological function.

Animals↗
PubMed1987

[Echocardiographic aspects of false intraventricular tendons].

A series of 4260 consecutive echocardiographic examinations, performed in 5 Cardiological Centers was examined, identifying 125 intraventricular false tendons (FTs) in 100 cases (55 normals and 45 with heart disease) of whom 31 were female and 69 male, aged 3 to 82 years. An anatomo-morphological study was possible in 9 cases, dead for stroke or heart failure, on autopsy, and in 7, on heart surgery. A phonocardiogram was performed in all normals and in 20 patients. On echocardiography, FTs appeared as an echo-producing string-like structure, straight between the septum and the ventricular free wall, mobile during the cardiac cycle, without systolic thickening and any relation with the atrioventricular valvular apparatus. The prevalence of FTs was 2.3%; it was 3.2% to 5.3% in younger people. FTs were located in the right ventricle (4 cases), left ventricle (95 cases) or in both (1 case). Their site was left apical (45 FTs), right apical (2 FTs), right (3 FTs) and left (20 FTs), upper septum-to-free wall (55 cases). In 1 case hypertrophy of trabeculae of the left ventricle was detected. FTs were single (79 cases), double (19 cases), multiple (2 cases), short (42 cases), long (58 cases), thick (45 cases) and thin (55 cases). They showed a membrane-like motion (thick FTs-45 cases) and a valve-like motion (thin FTs-55 cases). Innocent murmur was detected in 50 of 55 normals and related to thin FTs. Of 16 cases examined anatomically and histologically, FTs were fibrous in their distal portion and fibro-muscular in the proximal one in 12 cases, whereas they were entirely fibrous-muscular in 4 cases. The site and location of FTs detected by echo were confirmed by anatomy in all cases. In 4 cases other 9 FTs, not detected on echocardiography, were found. These data suggest that echocardiography is a useful tool to detect intraventricular FTs and differentiate them from other echo-producing structures. Although a relationship between FTs and heart disease has not been found, their presence could be responsible of innocent murmur in many normal subjects.

Adolescent↗