In vivo analysis of the drosophila light-sensitive channels, TRP and TRPL.

We have tested the proposal that the light-sensitive conductance in Drosophila is composed of two independent components by comparing the wild-type conductance with that in mutants lacking one or the other of the putative light-sensitive channel subunits, TRP and TRPL. For a wide range of cations, ionic permeability ratios in wild type were always intermediate between those of trp and trpl mutants. Effective channel conductances derived by noise analysis in wild type were again intermediate (17 pS; c.f. 35 pS in trp and 4 pS in trpl) and also showed a complex voltage dependence, which was quantitatively explained by the summation of TRPL and TRP channels after taking their different reversal potentials into account. Although La3+ partially blocked the light response in wild-type photoreceptors, it increased the effective single channel conductance. The results indicate that the wild-type light-activated conductance is composed of two separate channels, with the properties of TRP- and TRPL-dependent channels as determined in the respective mutants.

Functional equivalence of native light-sensitive channels in the Drosophila trp301 mutant and TRPL cation channels expressed in a stably transfected Drosophila cell line.

Drosophila photoreceptors express two putative cation channels encoded by the transient receptor potential (trp) and trp-like (trpl) genes, which represent prototypical members of a novel family of phosphoinositide-regulated calcium influx channels. Mutations of both trp and trpl selectively abolish components of the light-sensitive current and, when heterologously expressed, both generate cation permeable conductances; however, a detailed comparison of recombinant and native channel properties is lacking. To more rigorously test the hypothesis that TRPL channels mediate one component of the light-sensitive current we have generated cell lines (Drosophila S2 cells) stably transfected with trpl cDNA and compared the recombinant channel properties with those of the light-sensitive conductance in situ in a Drosophila trp mutant under identical conditions. We found close correspondence in respect of a number of quantifiable biophysical parameters including: current voltage relationships, ionic selectivity, voltage independent block by external Mg2+ ions and effective single channel conductance and gating kinetics derived by noise analysis. Our estimate of 60-70 pS for channel conductance was confirmed directly in patch clamp recordings of single TRPL channels in S2 cells. These findings indicate that channels encoded by the trpl gene can completely account for the component of the light-sensitive conductance remaining in the trp mutant.

Human papillomavirus as expressed in cervical neoplasia: evolving diagnostic and treatment modalities.

Cervical carcinoma, a common form of cancer among women worldwide, is directly linked with human papillomavirus (HPV) infection. It is estimated that 20-30 million Americans have been infected with HPV, yet many women and health care providers have little knowledge of the etiology, diagnosis, and treatment of this infection. Only 30% of HPV infections are overt, recognized by women as genital warts. Subclinical infection accounts for 70% of HPV infections and, because it may cause cervical cancer, represents a major health problem for women. Dramatic advances in the diagnosis and treatment of HPV genital infection have occurred in the past decade. The epidemiology and risk factors, along with the efficacy, side effects, and cost-effectiveness of different diagnostic and treatment methods are discussed.

Single photon responses in Drosophila photoreceptors and their regulation by Ca2+.

1. Discrete events (quantum bumps) elicited by dim light were analysed in whole-cell voltage clamp of photoreceptors from dissociated Drosophila ommatidia. Bumps were automatically detected and analysed for amplitude, rise and decay times, and latency. 2. The bump interval and amplitude distributions, and the 'frequency of seeing' curve conformed to Poisson predictions for the absorption of single photons. 3. At resting potential (-70 mV), bumps averaged 10 pA in peak amplitude with a half-width of ca 20 ms, representing simultaneous activation of ca 15 channels. 4. The macroscopic response to flashes containing up to at least 750 photons were predicted by the linear summation of quantum bumps convolved with their latency dispersion. 5. Bump duration was unaffected by lowering the extracellular Ca2+ concentration ([Ca2+]o) from 1.5 to 0.5 mM, but increased >10-fold between 0.5 mM Ca2+ and 0 Ca2+. Bump amplitude was constant over the range 1.5-100 microM, but decreased ca 5- to 10-fold at lower Ca2+ concentrations. Bump latency increased by ca 50 % between 1.5 mM and 100 microM Ca2+o but returned to near control levels in Ca2+-free solutions. At intermediate [Ca2+]o bumps were biphasic with a slow rising phase followed by rapid amplification and inactivation. This behaviour was mimicked in high [Ca2+]o by internal buffering with BAPTA, but not EGTA. This suggests that Ca2+ influx through the light-sensitive channels must first raise cytosolic Ca2+ to a threshold level before initiating a cycle of positive and negative feedback mediated by molecular targets within the same microvillus. Quantum bumps in trp mutants lacking the major class of light-sensitive channel were reduced in size (mean 3.5 pA) representing simultaneous activation of only one or two channels; however, a second rarer (10 %) class of large bump had an amplitude similar to wild-type (WT) bumps. Bumps in trpl mutants lacking the second class of light-sensitive channel were very similar to WT bumps, but with slightly slower decay times. In InaDP215 mutants, in which the association of the TRP channels with the INAD scaffolding molecule is disrupted, bumps showed a defect in quantum bump termination, but their amplitudes and latencies were near normal.

Factors influencing the caffeine test for cytochrome P 448-dependent liver function.

Liver functions in patients with liver disease can be estimated by caffeine clearance. Our data, however, demonstrate the additional influence of factors other than liver disease on the caffeine test. Smoking enhances caffeine clearance in both healthy volunteers and patients with severe hepatic disorders, whereas co-medication with mexiletine strongly inhibits caffeine elimination.