Biomedical subjects

F Sesti

Publications and source records attributed to F Sesti.

At least 37 records · Page 2Linked to original sources

PubMed1995

The multi-ion nature of the cGMP-gated channel from vertebrate rods.

1. Native cGMP-gated channels were studied in rod outer segments of the larval tiger salamander, Ambystoma tigrinum. The alpha-subunit of the cGMP-gated channel, here referred to as the wild type (WT), and mutant channels were heterologously expressed in Xenopus laevis oocytes. These channels were studied in excised membrane patches in the inside-out configuration and were activated by the addition of 100 or 500 microM cGMP. The current carried by monovalent cations was measured under voltage-clamp conditions. 2. In the presence of 110 mM Na+ in the extracellular medium and different amounts of Na+ in the intracellular medium, the I-V relations of the native channel could be described by a single-site model with a profile of Gibbs free energy with two barriers and a well. A similar result was obtained in the presence of 110 mM Li+ in the extracellular medium and different amounts of Li+ in the intracellular medium. The well depth was 1.4RT (where R is the gas constant and T is the absolute temperature) for both Li+ and Na+. 3. The I-V relations of the native channel in the presence of 110 mM Na+ on one side of the membrane and 110 mM Li+ on the other side could not be described by the same single-site model with identical values of barriers and well obtained in the presence of Li+ or Na+ alone: the well for Li+ had to be at least 4RT. 4. In the presence of mixtures of 110 mM Li+ and Cs+ on the cytoplasmic side of the membrane, an anomalous mole fraction effect was observed both in the native and the WT channel. No anomalous behaviour was seen in the presence of Li(+)-Na+ and Li(+)-NH4+ mixtures. 5. The anomalous mole fraction effect with mixtures of Li+ and Cs+ was not observed in the channel where glutamate 363 was mutated to a glutamine (E363Q) or an asparagine (E363N). When glutamate 363 was mutated to an aspartate (E363D), the anomalous mole fraction effect with mixtures of Li+ and Cs+ was still observed, although significantly reduced. 6. When lysine 346, arginine 369, aspartate 370 and glutamate 372 were neutralized by mutation to glutamine, the ion permeation through the mutant channels and the WT channel had largely similar properties.(ABSTRACT TRUNCATED AT 400 WORDS)

Ambystoma↗

PubMed1995

A 240 kDa protein represents the complete beta subunit of the cyclic nucleotide-gated channel from rod photoreceptor.

The cyclic nucleotide-gated channel from rod photoreceptors is composed of two distinct subunits (alpha and beta). The properties of the alpha subunit, which can form functional channels by itself, are modified by coexpression with a homologous polypeptide, designated the beta subunit. However, the alpha subunit from rod photoreceptor membranes copurifies with a 240 kDa protein that is significantly larger than this putative beta subunit. We now demonstrate by peptide sequencing and by cloning and functional expression of cDNA that the 240 kDa protein represents the complete beta subunit with an unusual bipartite structure. The N-terminal part is essentially identical to a glutamic acid-rich protein (GARP), whereas the C-terminal part is highly homologous to the previously cloned human "beta subunit." Expression of the complete beta subunit in HEK 293 cells results in a polypeptide with the same apparent molecular weight as the 240 kDa protein of the native rod channel. Coexpression of the alpha subunit with the full-length beta subunit yields hetero-oligomeric channels with properties characteristic of the native channel.

Amino Acid Sequence↗

PubMed1994

Gating, selectivity and blockage of single channels activated by cyclic GMP in retinal rods of the tiger salamander.

1. Patches in the inside-out configuration were excised from the membrane of outer and inner segments of the larval tiger salamander, Ambystoma tigrinum. The current flowing through single channels opened by cyclic GMP was studied with the voltage clamp technique. 2. Amplitude histograms of current recordings from patches containing only one flickering channel, excised from the inner segment and in the presence of 100 microM cyclic GMP, could be fitted by a theoretical scheme in which the single channel conductance was at least 55 pS at +40 mV and at least 45 pS at -40 mV. The mean open time was no longer than the time constant of our recording system, about 35 microseconds. Similar results were obtained by analysis of the amplitude histograms of patches from the outer segment containing many channels, and in the presence of 1-5 microM cyclic GMP. 3. In membrane patches excised from the outer segment, reducing the temperature from 24 to 8 degrees C did not reduce the flickering, but changed the amplitude histograms of current fluctuations activated by 1 microM cyclic GMP in a way consistent with a decrease of 50% in the single channel conductance and a decrease of 50% in the open probability. 4. In the presence of 1 microM cyclic GMP at +60 mV, when Na+ was replaced by NH4+ or K+, brief outward current transients flowing through single channels were observed. When Na+ was replaced with Li+, Rb+ or Cs+, current transients were very small. 5. The shape of the power spectrum of current fluctuations induced by 1 microM cyclic GMP at +60 mV did not change when the permeating ion was Na+, K+ or NH4+. Analysis of the amplitude histogram did not show any effect of the tested monovalent cations on the open probability or on channel gating. At +60 mV, the estimated single channel currents were at least 4, 2.8 and 2 pA for NH4+, Na+ and K+ respectively. 6. The addition of 0.5 or 1 mM Ca2+ to the medium bathing the cytoplasmic side of the membrane greatly reduced the frequency of openings, but single channel activity could still be observed. The blocking effect of 1 mM Ca2+ on the channel activity induced by 2 microM cyclic GMP could be counterbalanced by increasing the cyclic GMP concentration. The addition of 0.5 or 1 mM Ca2+ did not change the shape of power spectra obtained at membrane voltages between -100 and +100 mV.(ABSTRACT TRUNCATED AT 400 WORDS)

Ambystoma↗

PubMed1994

Efficacy of CO2 laser surgery in treating squamous intraepithelial lesions. An analysis of clinical and virologic results.

This paper reports the clinical and virologic results of CO2 laser treatment for squamous intraepithelial lesions in 154 patients. On the basis of cervical canal involvement, vaporization or conization was performed. Failure rates following the first and second treatments were 4.5% and 0%, respectively. However, human papillomavirus persistence in several women with completely normal follow-up suggests that one of the possible mechanisms of failure could be reexposure of the healing area to a viral reservoir within the "normal" epithelium.

Adult↗

PubMed1993

Single-channel properties of cloned cGMP-activated channels from retinal rods.

Single-channel properties of a cloned channel activated by cyclic GMP have been analysed. The mRNA encoding for the channel was injected into oocytes of Xenopus laevis and the current flowing through a single ionic channel activated by cGMP was studied in excised patches under voltage-clamp conditions. The ionic channel activated by cGMP had a single-channel conductance of 32 +/- 2 pS at +120 mV and 25 +/- 4 pS at -120 mV, and its conductance was not significantly affected by increasing the cGMP concentration from 20 microM to 200 microM. The single-channel currents in the presence of NH+4, Na+, K+, Li+ and Rb+ in the medium bathing the cytoplasmic side of the membrane at +140 mV were 5.3, 4.7, 3.8, 1.3 and 0.8 pA, respectively. The single-channel current in the presence of Cs+ was less than 0.5 pA. Ca2+ and Mg2+ (both 0.5 mM) in the presence of 100 microM cGMP did not appreciably affect the channel activity at membrane potentials more negative than -80 mV, whereas at +100 mV they reduced the single-channel conductance by about threefold. The ionic selectivity and the blockage by divalent cations of the native channel found in amphibian rods and in the cloned channel from bovine rods are quite similar. However, the cloned channel has well-resolved openings, especially at positive membrane voltages, whereas the native channel is characterized by a continuous flickering between the open and closed state.

Animals↗

PubMed1992

Different channel-gating properties of two classes of cyclic GMP-activated channel in vertebrate photoreceptors.

We report that two types of cGMP-activated channel coexist in the photoreceptor plasma membrane, with the most commonly encountered class appearing broadly similar to the channel reported in previous patch-pipette experiments. However, we find that flickering of this channel between the open and closed states is so rapid that a discrete single-channel conductance cannot unequivocally be resolved; the occurrence of flickering is largely independent of membrane voltage and of the presence of cytoplasmic Ca2+ or Mg2+. In recordings from the inner segment we occasionally find a second class of cGMP-gated channel, with activity resembling that reported for cloned channels. This channel does not flicker, but instead exhibits distinct open-close transitions. Our results suggest that the predominant form of channel in vivo differs significantly from cloned channels, and that its gating properties are not as simple as reported previously.

Ambystoma↗

PubMed1992

The prevalence of HPV16DNA in normal and pathological cervical scrapes using the polymerase chain reaction.

Human papillomavirus (HPV) has been implicated in the development of cervical cancer. Newly developed molecular techniques have facilitated HPV identification and typing of cervical lesions. Several studies have suggested a strong correlation between HPV16 and intraepithelial cervical neoplasia. However, there is no agreement on this point since HPV16 is detected also in normal cervical tissue. We have amplified the L1 region of HPV16 DNA using the polymerase chain reaction (PCR) technique and analyzed the HPV16 prevalence in cytological scrapes of 201 Italian sexually active patients. One hundred twenty-four of these women had normal cytologic and colposcopic examination, while seventy-seven women had normal or abnormal cytology and a cervical lesion detectable by colposcopy. Within this latter group, 25 of 77 women (32.4%) were positive for HPV16 DNA, compared to 11 of 124 samples (8.87%) from women with normal cytology and colposcopy. The present results confirm the high efficiency of the PCR technique in detecting HPV16 DNA from cervical scrapes and suggest that this analysis should become a method of choice in clinical studies.

Adult↗

PubMed1991

Role of microcolposcopy in the diagnostic evaluation of cervical pre-invasive lesions.

The present clinical study was undertaken to assess and compare the value of microcolposcopy and endocervical curettage in the diagnostic workup of patients with abnormal cervical lesions. Microcolposcopic findings were well correlated to histology both on directed biopsy and endocervical curettage specimens. Therefore, both microcolposcopy and endocervical curettage are useful procedures to explore the endocervical mucosa. Microcolposcopy should be mainly indicated in those cases where colposcopy has failed to show any lesion, or when colposcopy is unsatisfactory.

Colposcopy↗

PubMed1991

Cytohistology, colposcopy and in situ hybridization in cervical preneoplastic lesions: a correlative study.

Formalin-fixed, paraffin-embedded cervical tissues from 106 patients which exhibited a colposcopically atypical transformation zone, were examined for the presence of HPV DNA by in situ hybridization using biotin-labeled HPV 6/11 and 16/18 DNA probes. From the comparative study between histologic, cytologic, colposcopic findings and virologic results it is confirmed that HPV 6/11 DNA is detected more frequently in the less severe lesions, whereas HPV 16/18 DNA is predominantly found in the most severe dysplastic lesions.

Cervix Uteri↗

PubMed1991

Carcinoma of the vulva with sarcomatoid features: a case report with immunohistochemical study.

A tumor of the vulva with sarcomatoid features was studied by immunocytochemistry to characterize the phenotype of the spindle-shaped and giant cells. Sarcomatoid-looking cells were positive for intermediate filament keratin polypeptides of stratified epithelium. These results favor histogenesis of the sarcomatoid-looking cells from a metaplastic alteration of the malignant squamous component.

Aged↗

PubMed1990

[Medical treatment of pelvic inflammatory disease. A clinical study on the therapeutic effectiveness of piperacillin + erythromycin and of piperacillin + clindamycin + gentamycin].

The aim of the present clinical study was to evaluate the therapeutic effectiveness of two different antibiotic combinations (piperacillin + erythromycin and piperacillin + clindamycin + gentamycin) in the medical treatment of patients with pelvic inflammatory disease, respectively at the II and III stage. The findings confirm the therapeutic value and the low toxicity of both pharmacological regimens.

Clindamycin↗

PubMed1990

Role of endocervical curettage in the diagnostic workup of preinvasive cervical lesions.

The aim of the present study was to evaluate the clinical value of endocervical curettage in the diagnostic workup of patients with colposcopically suspect lesions, by correlating the findings of colposcopically directed biopsy with the results of endocervical curettage in patients with both satisfactory and unsatisfactory colposcopic examination. Our results (positive curettage findings in 55.6% of the patients with unsatisfactory colposcopy and in 16.7% of the patients with satisfactory colposcopy) indicate that endocervical curettage could be a useful guide to correct management.

Biopsy↗

PubMed1989