Cationic amino acid fluxes beyond the proximal convoluted tubule of rat kidney

To investigate the fluxes of cationic amino acids beyond the proximal convolution, we micropunctured and microperfused superficial tubules of male Wistar rats in vivo et situ. In free-flow micropuncture experiments, the concentrations of endogenous L-arginine⁺, [Arg], and of intravenously infused L-homoarginine⁺, [HoArg], were determined by HPLC. Fluorescein isothiocyanatelabeled inulin was detected on-line in the same tubular fluid samples. To determine undirectional fluxes, radiolabeled Arg and inulin were (1) microperfused through short loops of Henle and (2) microinfused into different tubule segments to measure urinary recovery of the radiolabel. At a mean [Arg]_plasma of 116 mol/l, [Arg] was 9.3 mol/l in the late proximal tubule (LPT), and 35.6 mol/l in the early distal tubule (EDT) corresponding to fractional deliveries (FD) of 0.055 in LPT and 0.078 in EDT. Fractional urinary excretion (FE) of Arg was 0.00033 (P<0.05 vs FD_EDT). Infusion of HoArg (2.5 or 7.5 mol/min) led to respective mean [HoArg]_plasma values of 1.44 and 3.73 mmol/l, and resulted in respective FD_LPT values for HoArg of 0.23 and 0.53, respective FD_EDT values of 0.29 and 0.41, and finally, respective FE values for HoArg of 0.25 and 0.58. When short loops of Henle were microperfused with 1 or 50 mmol/l [¹⁴C]Arg (+[³H]inulin), fractional recovery (FR) of ¹⁴C (relative to inulin) in the EDT was 0.13 and 0.36, respectively. During microinfusion of radiolabeled Arg (1 or 50 mmol/l) and inulin into LPT, the urinary FR of the radiolabel was 0.14, or 0.59, respectively. If 0.007, 1 or 50 mmol/l radiolabeled Arg were microinfused into EDT, the respective urinary FR of the radioactivity was 1.02, 1.10, or 1.01. Microperfusion of microinfusion of 1 mmol/l [¹⁴C]Arg plus 50 mmol/l HoArg resulted in a FR_EDT of ¹⁴C of 0.43 (loop, perfusion) and an FE for ¹⁴C of 0.69. Five conclusions can be drawn. First, cationic amino acids can enter and leave the lumen of short loops of Henle through specific carrier(s) at high rates, although, secondly, net transport is small or absent. Thus, medullary tubule cells can be supplied with Arg from the lumen of short loops of Henle for urea and nitric oxide production. Thirdly, the distal convolution of superficial nephrons and the collecting duct are not permeable to Arg. Thus, fourthly, the difference between FD_EDT and urinary FE of Arg must be explained by an inter-nephron heterogeneity between deep and superficial nephrons. Finally, the process responsible for the different Arg handling in deep nephrons is not accessible to HoArg or, if so, it is saturated at millimolar concentrations.     

Concomitant radiochemotherapy with 5-FU and cisplatin for invasive bladder cancer

Purpose

To evaluate acute toxicity and efficacy of simultaneous radiochemotherapy for invasive urothelial cancer of the bladder.

Patients and Methods

From September 1993 to July 1997,61 patients with invasive bladder cancer were treated with a transurethral resection (TURB) followed by radiochemotherapy (RCT). Twenty-five received a combination of 5-FU and cisplatin. The prescribed doses were 600 mg/m² 5-FU daily as continuous infusion over 5 days each in the 1st and 5th treatment week and 20 mg/m² cisplatin daily at the same days as a short infusion. The pelvis was irradiated with 54 Gy, the bladder with 59.4 Gy and the paraortic nodes in 7 cases with 45 Gy, respectively. Six to 8 weeks after RCT a second TURB was performed for reasons of restaging.

Results

Twenty out of 25 patients received at least 80% of the prescribed chemotherapy, in 13 cases the full dose could be given. Gastrointestinal toxicity of Grade I and II occurred in 10 cases, 1 patient developed severe diarrhea (Grade VI). After the 1st course of chemotherapy 7 patients had leucoor thrombopenia of Grade III. One patient had a leucopenia of Grade IV. After the 2nd course 4 patients developed Grade III leuko- and thrombopenia, 1 of Grade IV. Two Grade II anemia were found. All more severe toxicities and necessary dose reductions were related to radiation of the paraaortic nodes. No life threatening infections, bleedings or cardiotoxicity was found. Restaging TURBs resulted in 22 complete remissions, 1 patient had a de-novo-carcinoma (Tis) at this time, 2 were non-responders (8%). After a median follow-up of 38 months 20 patients are alive (80%).

Conclusions

1. If irradiation of paraaortic nodes is necessary, 5-FU should not be applied, because the gastrointestinal toxicity is too extensive. In all other cases side effects are tolerable and can be managed by supportive care. 2. The first results are promising and should be evaluated in a prospective study.     

An Early Onset Rehabilitation Program for Children and Adolescents after Traumatic Brain Injury (TBI): Methods and First Results

Survived traumatic brain injuries (TBI) are one of the most serious challenges to the patient's future life. Recent literature increasingly questions the long believed protective effects of functional cerebral plasticity in children. Although TBI in children and adolescents is frequent, they are less frequently admitted to rehabilitation centers as in-patients than adults. This emphasizes the role of out-patient treatment. The progressing study described here aims to achieve a contribution to a comprehensive approach in TBI-rehabilitation for youngsters. A two-stage multimethodal program, starting with stimulation in coma while the patient is on the intensive care unit, and neuropsychological therapy after regaining consciousness is to be evaluated in a controlled, prospective and randomized study. After including nearly 50 % of the planned sample (100 persons), some preliminary results can be mentioned with all applicable caution. The effectiveness of the applied therapy can be stated here with respect to the posttraumatic development of intellectual abilities in the 6- and 12 months follow ups. Moreover, in the control group development of psychopathological alterations was found to a considerable degree and also lower ratings in a quality of life questionnaire, compared to the experimental group. It is expected to prove these differences statistically, after the total sample has been included, and thus equal distributions have been achieved in all predictive variables.     

Effects of local MAO inhibition in the locus coeruleus on extracellular serotonin and 5-HIAA during exposure to sensory and cardiovascular stimuli

Previously, we have shown that in the presence of pargyline the release of serotonin (5-HT) in the locus coeruleus is modulated by various sensory stimuli and blood pressure fluctuations. The aim of the present study was to investigate whether local inhibition of monoamine oxidase (MAO) influences basal and stimulus-induced release of 5-HT in the locus coeruleus. For this purpose, the locus coeruleus was superfused in the absence and in the presence of the MAO inhibitor pargyline. Additionally, we examined whether the release of the 5-HT metabolite 5-hydroxy-indole acetic acid (5-HIAA) in the locus coeruleus is altered in response to stimuli. The locus coeruleus of the conscious rat was superfused through a push-pull cannula with artificial cerebrospinal fluid (CSF). 5-HT and 5-HIAA were determined in the superfusate. The basal release rate of 5-HT and the basal outflow of 5-HIAA averaged 2.0 fmol/min and 69 fmol/min, respectively. The basal release rate of 5-HT and the 5-HIAA outflow were tetrodotoxin (TTX)-sensitive. In the absence of pargyline, the sensory stimuli noise stress or tail pinch, applied for 10 min, increased 5-HT and 5-HIAA outflow by 50–70%. In contrast, an experimentally induced rise in blood pressure for 10 min enhanced 5-HT release by 50%, but had no effect on 5-HIAA outflow. The release of 5-HT and/or 5-HIAA elicited by sensory stimuli or a blood pressure rise was abolished by TTX. Addition of pargyline to the CSF enhanced 5-HT release fourfold and slightly decreased 5-HIAA outflow. These levels remained stable throughout the entire observation period of 8 h. In the presence of pargyline, 5-HT release elicited by noise, tail pinch and increase in blood pressure was enhanced. It is concluded that superfusion with pargyline enhances 5-HT release and reduces 5-HIAA outflow in the locus coeruleus. Furthermore, the ability of sensory stimuli and baroreceptor activation to enhance 5-HT release is preserved during a prolonged pargyline-induced increase in extracellular 5-HT. Since sensory stimuli enhanced, while baroreceptor activation did not influence 5-HIAA outflow, 5-HIAA is not a reliable index for short-term changes in the activity of serotonergic neurons in the locus coeruleus. Received: 13 July 1998 / Accepted: 10 December 1998     

Intensity dependence of auditory evoked potentials (AEPs) as biological marker for cerebral serotonin levels: effects of tryptophan depletion in healthy subjects

Rationale: The intensity dependence of the auditory evoked potentials (AEP) has been suggested to be a specific biological marker of central serotonergic activity. Objective: While previous studies used circumstantial evidence to support this hypothesis, we manipulated (decreased) cerebral levels of serotonin directly by using tryptophan depletion. Methods: Twelve healthy young subjects were investigated using placebo and two different amino acid mixtures in a double blind cross over design on three different occasions. AEPs recorded during tryptophan depletion were analyzed by dipole analysis and regional sources using methods published in the literature. Results: For none of the mixtures a significant effect of tryptophan depletion was found. There was a trend towards reduced intensity dependency after tryptophan depletion, especially in the right hemisphere. This reduction correlated with the amount of reduced tryptophan in plasma. Conclusions: The results indicate, in contrast to earlier indirect studies, that the intensity dependence of AEPs is not a specific marker of central serotonergic activity. Received: 8 March 1999 / Final version: 25 May 1999     

Clomipramine and Sexual Function in Men with Premature Ejaculation and Controls

Purpose

We determined whether clomipramine taken as needed increases ejaculation latency in men with premature ejaculation and controls.

Materials and Methods

The study included 8 patients with primary premature ejaculation, 6 with premature ejaculation and erectile dysfunction, and 8 controls. A prospective, double-blind, placebo controlled, crossover design was used that included 2, 3-week periods with clomipramine and placebo. During treatment phases subjects took either 25 mg. clomipramine or placebo as needed, that is 12 to 24 hours before anticipated sexual activity (coitus or masturbation). Subjects also visited the laboratory during these phases for evaluation of sexual response using visual erotic stimulation with and without vibration to the penis. Daily logs of sexual activities were maintained during treatment phases.

Results

Clomipramine significantly increased the latency to ejaculation during sexual activity (coitus or masturbation) from approximately 2 to 8 minutes in men with primary premature ejaculation. There were no significant effects in controls and men with premature ejaculation plus erectile dysfunction. Laboratory assessment indicated that men with primary premature ejaculation were better able to control ejaculatory response with clomipramine therapy. In these men clomipramine also resulted in increased satisfaction with sex life and relationship. Clomipramine inhibited nocturnal penile tumescence in all subjects.

Conclusions

Clomipramine (25 mg. as needed) effectively increases ejaculatory latency in men with primary premature ejaculation, while treatment is not effective in those with premature ejaculation and erectile dysfunction.     

Radical cystectomy with or without adjuvant polychemotherapy for non-organ-confined transitional cell carcinoma of the urinary bladder: Prognostic impact of lymph node involvement

Objectives

To analyze the effectiveness of adjuvant polychemotherapy after radical cystectomy for nonorgan-confined transitional cell bladder cancer (Stages pT3b, pT4a, and/or pN1 or pN2).

Methods

Of 166 consecutive patients undergoing cystectomy at two institutions from 1987 to 1993, 80 received adjuvant polychemotherapy with methotrexate, vinblastine, and cisplatin plus doxorubicin (MVAC) or epirubicin (MVEC), whereas 86 had cystectomy only. The patients were evaluated for relapse-free survival and length of progression-free interval on the basis of follow-up data obtained in 1995 and 1996.

Results

Kaplan-Meier analysis revealed a significantly higher progression-free rate for patients after adjuvant chemotherapy (P=0.0002, log-rank test). With and without adjuvant chemotherapy, prognosis declined in a stepwise manner, depending on the extent of lymph node involvement. Nevertheless, the superior prognosis of the chemotherapy group could be demonstrated at each lymph node stage. Of the 166 patients, 49 had initially entered a prospective trial comparing adjuvant with no adjuvant treatment. That study was discontinued in December 1990 after an interim analysis revealed a significant prognostic advantage in favor of the 26 patients randomized to receive chemotherapy compared with the 23 control patients. Current follow-up data continue to demonstrate a significant improvement in progression-free survival in favor of patients randomized to receive adjuvant chemotherapy (P=0.0040). The follow-up period of patients living free of disease ranges from 58 to 96 months.

Conclusions

Adjuvant chemotherapy with MVAC/MVEC leads to significant prolongation of relapse-free survival and improvement of the definitive cure rate after radical cystectomy for locally advanced transitional cell carcinoma of the urinary bladder.     

Absorption Enhancing Effect of Cyclodextrins on Intranasally Administered Insulin in Rats

The absorption enhancing effect of -, -, and -cyclodextrin (CD), dimethyl--cyclodextrin (DMCD), and hydroxypropyl--cyclodextrin (HPCD) on intranasally administered insulin was investigated in rats. Coadministration of 5% (w/v) DMCD to the insulin solution resulted in a high bioavailability, 108.9 ± 36.4% (mean ± SD, n = 6), compared to i.v. administration, and a strong decrease in blood glucose levels, to 25% of their initial values. Coadministration of 5% -CD gave rise to an insulin bioavailability of 27.7 ± 11.5% (mean ± SD, n = 6) and a decrease in blood glucose to 50% of its initial value. The rate of insulin absorption and the concomitant hypoglycemic response were delayed for the -CD-containing solution as compared to the DMCD preparation. The other CDs, HPCD (5%), -CD (1.8%), and -CD (5%), did not have significant effects on nasal insulin absorption. DMCD at a concentration of 5% (w/v) induces ciliostasis as measured on chicken embryo tracheal tissue in vitro, but this effect is reversible. In conclusion, DMCD is a potent enhancer of nasal insulin absorption in rats.     

Left vagus nerve stimulation suppresses experimentally induced pain

OBJECTIVE: To test whether electric stimulation of the vagus nerve has an antinociceptive effect in humans. BACKGROUND: In a variety of animal studies, vagus nerve stimulation was shown to inhibit nociceptive behavior as well as electric responses of spinal nociceptive neurons. In humans, chronic left vagus nerve stimulation is used to treat pharmacologically refractory epilepsy. METHODS: The authors investigated experimental pain in 10 patients with seizures before and twice after implantation of a vagus nerve stimulator by using different controlled stimuli, including noxious heat, tonic pressure, and short impact. Pain was quantified on a visual analogue scale. Twelve nonepileptic age- and gender-matched individuals served as control subjects. RESULTS: Vagus nerve stimulation reduced increasing pain associated with trains of five consecutive stimuli at 1.5-second intervals ("wind-up"; p < 0.001). In a similar manner, pain on tonic pressure was reduced by vagus nerve stimulation (p < 0.03). Pain associated with single-impact stimuli as well as heat pain thresholds were unaltered under vagus nerve stimulation. Thus, vagus nerve stimulation led to pain relief predominantly in experimental procedures in which pain magnitude was amplified by central processing. The antinociceptive effect was independent of the acute on-off cycles of vagus nerve stimulation. CONCLUSIONS: Vagus nerve stimulation is effective in reducing pain in humans. In humans, the antinociceptive effect might rely on central inhibition rather than alterations of peripheral nociceptive mechanisms. These results indicate a promising, potential future role of vagus nerve stimulation in pain treatment.