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Biomedical subjects

P Jonas

Publications and source records attributed to P Jonas.

At least 91 records · Page 5Linked to original sources
PubMed1989

Single-channel recording in myelinated nerve fibers reveals one type of Na channel but different K channels.

Amphibian myelinated nerve fibers were treated with collagenase and protease. Axons with retraction of the myelin sheath were patch-clamped in the nodal and paranodal region. One type of Na channel was found. It has a single-channel conductance of 11 pS (15 degrees C) and is blocked by tetrodotoxin. Averaged events show the typical activation and inactivation kinetics of macroscopic Na current. Three potential-dependent K channels were identified (I, F, and S channel). The I channel, being the most frequent type, has a single-channel conductance of 23 pS (inward current, 105 mM K on both sides of the membrane), activates between -60 and -30 mV, deactivates with intermediate kinetics, and is sensitive to dendrotoxin. The F channel has a conductance of 30 pS, activates between -40 and 60 mV, and deactivates with fast kinetics. The former inactivates within tens of seconds; the latter inactivates within seconds. The third type, the S channel, has a conductance of 7 pS and deactivates slowly. All three channels can be blocked by external tetraethylammonium chloride. We suggest that these distinct K channel types form the basis for the different components of macroscopic K current described previously.

Animals↗
PubMed1989

[Percutaneous vertebroplasty in the treatment of metastases. Technic and results].

The authors studied 20 patients with vertebral metastases. They injected in these metastases orthopaedic cement by a percutaneous technique under local anesthesis. The results are good for 16 patients, nul for 2 patients and we observed 2 complications. The authors conclude that the best indication is the painy somatic lysis of a vertebra without peri-radicular tumor.

Adult↗
PubMed1989

Clinical application and results of ureteral ileal substitution.

Three cases in which an ileal segment was used to replace the ureter are reported. Indications included irreparable damaged ureters in two of the cases and recurrent calculi with extrinsic ureteral obstruction in one. Excellent results were noted, and at 18 months follow-up renal function was unchanged, pyelographic appearance was improved and the patient with stone disease had no recurrent or residual stones.

Anastomosis, Surgical↗
PubMed1989

[Optical assistance in guiding punctures under x-ray computed tomographic control].

The authors describe a new technic for realisation of CT-guided punctures. This original device uses a buna tourniquet placed on the table for drawing on the skin the site of puncture and a movable light-visor for guiding the needle during the puncture. The advantages of this device are: no using of disposable or sterilised material; total freedom of the hand during the puncture; to be simple and quick.

Biopsy, Needle↗
PubMed1988

Long-term followup of patients less than 30 years old with transitional cell carcinoma of bladder.

A review of our records between 1970 and 1986 identified 22 patients with transitional cell carcinoma of the bladder who were less than 31 years old. Of these patients 7 were less than 20 years old (group 1) and 15 were 20 to 30 years old (group 2). The tumors usually were of low grade and low stage. Patients in group 1 had no recurrences, whereas 6 patients (40 per cent) in group 2 had recurrences. Upstaging occurred in 2 patients with tumor recurrence. It would appear that while transitional cell carcinoma of the bladder in patients less than 20 years old has a more favorable prognosis, in patients 20 to 30 years old the prognosis is poorer and similar to that observed in older patients.

Adolescent↗
PubMed1988

The transvesical approach for the removal of distal ureteral calculi.

Our experience with a modification of transvesical ureterolithotomy in 12 patients in whom endourological extraction failed is presented and the technique is described. Successful removal of stones was achieved in all patients with 1 significant postoperative complication of a perivesical hematoma, which was drained percutaneously. Excretory urography and voiding cystourethrography at 3 months and 1 year postoperatively demonstrated no ureteral stricture or vesicoureteral reflux. When removal of distal ureteral stones by endourological means or extracorporeal shock wave lithotripsy fails, we recommend transvesical ureterolithotomy as an easy and rapid approach that necessitates minimal dissection away from blood vessels and avoids manipulation or displacement of the ureteral orifice.

Adult↗
PubMed1987

Urethral strictures in boys.

While common in adult males, urethral strictures are comparatively rare in boys. We report our experience with this condition in 19 boys. Ten of the strictures were iatrogenic, seven traumatic, and three inflammatory in origin. Dilation is reportedly unsatisfactory for the management of most urethral strictures in children. In our series, however, 9 patients (47.3%) underwent urethral dilation as the only definitive form of treatment, while urethroplasty was successfully performed in the other 10 cases.

Child↗
PubMed1987

Vesicoureteral reflux in adults: a review of 95 patients.

Ninety-five adult patients with primary vesicoureteral reflux were reviewed concerning the presenting symptoms, radiological findings, associated renal damage, treatment and results of follow-up. We found a relatively high incidence of reflux in adult males. Although urinary tract infection and flank pain were the most common presentation, others had a wide variety of complaints not directly attributable to reflux. Renal anomalies were present in 37 patients. We found surgical correction of reflux useful in preventing infection, and recommend it especially in young women who may become pregnant.

Adolescent↗
PubMed1986

Toxin gamma of the scorpion Tityus serrulatus modifies both activation and inactivation of sodium permeability of nerve membrane.

The effects of the major neurotoxic fraction isolated from scorpion venom of Tityus serrulatus, TiTx gamma, on peripheral nerve membrane of Xenopus laevis were studied under current- and voltage-clamp conditions. 700 nmol/l TiTx gamma depolarized the membrane and induced spontaneous activity (150 s-1, maximum value), which ceased within a few minutes. It reduced the amplitude of the action potentials from 109 mV to 52 mV and increased their duration from 1.25 ms to 4.5 ms. 440 nmol/l TiTx gamma induced inward Na current flow at resting potential. The descending branch of the Na current-voltage curve was flattened and shifted approximately 10 mV to more negative potentials. Maximum Na permeability was reduced to about 20%. Both development of and recovery from inactivation of Na permeability were slowed. The steepness of the steady-state inactivation curve was decreased, but the mid-potential changed only insignificantly. No prepulse was necessary to elicit either a shift of activation or an inward current at resting potential. Expressing the toxin effect either in terms of the decrease of Na peak current or of the slowing of inactivation, half-maximum effects were found with 0.3 +/- 0.1 and 3.7 +/- 0.7 mumol/l TiTx gamma, respectively.

Action Potentials↗
PubMed1986

Familial vesicoureteral reflux: a study of 16 families.

Siblings of patients with vesicoureteral reflux (VUR) are reported to have an increased incidence of reflux. We present 16 families with 33 affected children out of a total of 493 patients with VUR. Twenty-seven had urinary tract infection and 6 were asymptomatic and were examined because a sibling had VUR. Renal scarring was present in 19 cases; reflux was more marked and more often bilateral in the siblings than in sporadically affected children. In view of our findings we suggest that siblings of patients with VUR be screened early for reflux to prevent renal damage from untreated VUR.

Adolescent↗
PubMed1985

Neurobehavioral development following aluminum administration in infant rabbits.

Aluminum (Al) is known to be a neurotoxic agent in some species, inducing neurofibrillary tangles, dendritic atrophy, and behavioral deterioration, and has been implicated as a possible agent in human Alzheimer's disease and dialysis dementia. This study was conducted to assess the neurotoxic effects of Al in infant rabbits, and to compare the effects to those previously observed to follow exposure in the adult animal. Aluminum tartrate (2 microM) or physiologic saline was injected into the right lateral ventricle of 2-day-old (day P3) New Zealand white rabbits. The animals were trained in a step-down active avoidance task on P12 and retested 1 day later. They were killed on P20, and their hippocampal CA1 pyramidal cells examined for neurofibrillary tangles or prepared with the rapid Golgi stain for an examination of dendritic development. Additional animals were similarly infused with 1 or 3 microM Al for qualitative and some quantitative observations. No overt neurologic signs were observed in the 1- or 2-microM groups, however, most of the 3-microM group died between P10 and P20. Although there were no significant differences between the 2-microM and control animals on either learning or retention of the active avoidance task, deficits in retention of the task were observed in the 3-microM group. Neurofibrillary tangles in CA1 pyramidal cells were observed with dosages of 1 microM and higher. In the 2-microM group, the pattern of dendritic arborization in CA1 pyramidal cells was consistent with that expected for cells retarded in their development. These results have implications in terms of developmental differences in the neurobehavioral effects of Al.

Aluminum↗