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Biomedical subjects

M Fraenkel

Publications and source records attributed to M Fraenkel.

8 recordsLinked to original sources
PubMed2006

Sex-steroid milieu determines diabetes rescue in pttg-null mice.

Male mice that are pttg-null develop sexually dimorphic diabetes with hypoinsulinemia secondary to reduced postnatal-cell proliferation and an inability to expand islet cell mass with aging. We therefore examined the effects of sex-steroid manipulation on diabetes development in pttg-/- male mice. Surgical gonadectomy was followed by implantation of 90-day slow-release pellets releasing 17beta-estradiol (0.36 mg/pellet), placebo or dihydrotestosterone (DHT; 12.5 mg/pellet). Mean fasting blood sugars at the end of the study were 414 +/- 54 mg/dl for pttg-/- controls and 371 +/- 14 mg/dl for pttg-/- mice gonadectomized and treated with DHT compared with 124 +/- 40 and 85 +/- 12 mg/dl in gonadectomized pttg-/- males treated with placebo or estradiol, respectively (P < 0.01 compared with control pttg-/-). Gonadectomy with and without estradiol treatment did not increase the very low circulating insulin levels in pttg-null males (fasting insulin 0.44 +/- 0.04 ng/ml in pttg-/- controls, 0.47 +/- 0.07 and 0.4 ng/ml in pttg-/- gonadectomized males treated with placebo or estradiol, respectively). Gonadectomy increased serum adiponectin levels (4.9 +/- 008 microg/ml in pttg-/- controls versus 13 +/- 0.08 and 7.5 +/- 0.6 microg/ml in pttg-/- gonadectomized males treated with placebo or estradiol, respectively; P < 0.001 and P < 0.05), accompanied by increased insulin sensitivity. The results show that gonadectomy delayed, and gonadectomy with additional estradiol treatment prevented, diabetes development in pttg-/- males, possibly through increased insulin sensitivity mediated by elevated serum adiponectin levels. Male-selective effects of disrupted beta-cell proliferation in the absence of pttg are restored by sex-steroid effects on peripheral insulin sensitivity.

Adiponectin↗
PubMed2001

Interband and intraband (Drude) contributions to femtosecond laser absorption in aluminum.

Theoretical and experimental investigations of the absorption in metallic aluminum of femtosecond-laser radiation pulses with peak intensity I0 less similar 10(15) W/cm(2) are reported. Energy balance equations are solved for electron and phonon subsystems, together with Helmholtz equation for the laser radiation. Expressions for the relaxation times as functions of electron and phonon temperatures are obtained, with no free parameters. Contrary to the assumption made in published studies, we find that the interband rather than the intraband (Drude) absorption plays the dominant role in the near infrared and throughout the visible region at low and moderate intensities. For 50 fs, 800 nm laser pulses the absorption in interband transitions dominates for intensities up to few times 10(13) W/cm(2). For such pulses, broadening of the parallel-band interband absorption line with the increase in electron and phonon temperatures results, for I0 < or =5 x 10(13) W/cm(2), in the decrease of the absorption coefficient compared to the room-temperature value. In this paper, we present both the first theoretical prediction and the first experimental observation of this phenomenon. Dielectric permittivity gradients within the skin layer also contribute to the decrease in absorption. The mechanisms of the lattice disordering are considered quantitatively, and it is shown that for I0 < 10(14) W/cm(2) melting does not occur in the laser-pulse duration. Experimental results are presented for 800 and 400 nm wavelengths. The agreement between the theory and the experiment is very good.

Journal Article↗
PubMed2000

Measurement of the energy penetration depth into solid targets irradiated by ultrashort laser pulses

The energy penetration depth of a short (100 fs) Ti-sapphire laser pulse (0.8 &mgr;m) of intensity 3x10(16) W/cm(2), in solid density materials has been measured. High-Z (BaF2) and low-Z (MgF2) solid layers targets were used. The penetration depth was determined from the measurement of the x-ray emission spectra, as a function of the target thickness. The investigation of these spectra showed that in the low-Z case, solid density material to a depth of 50 nm was heated to a peak electron temperature of approximately 150 eV. For the high-Z material, the penetration depth corresponding to this temperature exceeded 100 nm. This is evidence of a larger heat penetration depth in a high-Z material in comparison to a low-Z material. A model based on electron heat conduction is used to estimate the energy penetration depth. It is suggested that the larger heat penetration in high-Z material is due to heating of the material, caused by the radiation flux, generated by the electron heat conduction.

Journal Article↗
PubMed2000

Effect of four treatment variants on the functional and cosmetic state of mature scars.

A randomised, intra-individual, comparative study demonstrated that both qualitative improvements and significant changes in skin functional condition can be achieved in the tissue of older, mature scars. Four treatment modalities were studied in an intra-individual comparison involving 12 volunteers with 2.5 to 4-year-old scars. The treatments were: a self-adherent, hydroactive, polyurethane dressing alone; polyurethane plus compression; silicone sheeting plus compression; and compression alone. Evaluation criteria were changes in the microcirculation, roughness and the skin temperature of the scar tissue. All treatment modalities were found to have significant effects both on tissue function and scar tissue surface structure. The most pronounced effects were achieved with the combination of polyurethane dressing plus compression or silicone sheeting plus compression. The positive effect of the polyurethane dressing alone on scar tissue was even slightly superior to that of compression therapy alone.

Cicatrix↗
PubMed1990

On letting go: the patient, haemodialysis and opting out.

The title of this article refers not only to the patient who decides to let go of life, the quality of which on dialysis is such that death is preferable, but also to the family and the renal unit staff who have to let go of the patient who makes this decision. One such case is described in detail since the problem is not one restricted to the treatment of end-stage renal failure alone, but occurs more and more frequently in other branches of medicine and surgery.

Adaptation, Psychological↗