High resolution real-time ultrasonography in the localization of the undescended testis

In a prospective study ultrasound was compared to palpation in 41 instances in which a testis was not present in the scrotum. A testis was palpable in 20 of these instances and not palpated in 21. Of 20 palpable undescended testes 14 (70 per cent) were identified by ultrasound. Of the 21 instances in which a testis was not palpated 3 intra-abdominal and 5 inguinal testes were identified at exploration. One of these organs (an inguinal testis) was identified by ultrasound. Two false positive sonograms in which a gubernacular structure mimicked an undescended testis occurred. Sonography cannot satisfactorily stand alone as a screening modality in the management of the undescended testis.

Acute adrenal insufficiency as a complication of urological surgery

Acute adrenal insufficiency postoperatively is an uncommon problem and, if unrecognized, it may cause serious morbidity and can be fatal. It can occur as the result of acute bilateral adrenal hemorrhage associated with anticoagulation, inadvertent injury to or removal of a solitary adrenal gland, or postoperative stress in an individual with incipient adrenal insufficiency. Its manifestations, such as fever, tachycardia, hypotension, lethargy, abdominal pain and gastrointestinal dysfunction, mimic the other more common postoperative complications and compound the difficulty in establishing the correct diagnosis. Once the diagnosis is made the condition is readily managed successfully. We report 3 cases of acute adrenal insufficiency occurring after salvage cystectomy, ileal replacement of the ureter and retropubic prostatectomy, which illustrate the salient clinical features, problems in diagnosis and predisposing risk factors. All 3 patients survived once the diagnosis of adrenal insufficiency was made. These cases emphasize the need to be aware of the possibility of this complication to make the correct diagnosis and to institute proper treatment.

The role of ureteral peristaltic rate and bolus volume on increasing urine flow

Electromyogram (EMG) and bolus volume of ureteral peristalsis were measured during gradual and rapid urinary flow increase in mongrel dogs. In acute diuresis induced by furosemide, the ureteral peristaltic rate rose and then the bolus volume increased with a consequent increase of urine flow. During a course of gradually increasing urine secretion, the ureter showed varying responses in respect to peristaltic rate (i.e., increase, no change and decrease) but changes in the bolus volume consistently made up for the rate alterations, thereby eventually maintaining an efficient equilibrium of these two urodynamic parameters to effect an increase in urine flow. The ureteral peristaltic rate increases only several times in polyuria as compared to the rate in oliguria, whereas the bolus volume of urine increases by a factor of 100. This indicates that it is not so much the ureteral peristaltic rate as the bolus volume which plays a principal part in the transport of urine through the ureter.

Sphincteric action of the pelvicalyceal junction and pacemaker activity in human kidney

The effect of elevation of renal pelvic pressure on pacemaker activity was examined in 5 isolated human kidneys. Pressure fluctuations transmitted from renal pelvic contractions first appeared in pressure tracings from the upper renal calyx as renal pelvic pressure exceeded 25 cm H2O. This finding suggests that the pelvicalyceal junction acts as a sphincter which can withstand pelvic pressures of about 25 cm H2O. The upper renal calyx contracted rhythmically at a rate of 10 times per minute when the pelvic pressure was low. At high pelvic pressures, upper calyceal contraction frequency decreased although its rhythm remained regular. As renal pelvic pressure increased, the frequency of renal pelvic contractions increased to a level that corresponded in a 1:1 ratio with contractions of the upper calyx.

Effect of dibutyryl cyclic adenosine monophosphate on canine pelviureteral discharge potentials

An electromyographic study of the responses of the pelviureter to dibutyryl cyclic AMP was performed using isolated canine pelviureteral preparations. Dibutyryl cyclic AMP caused a marked increase in the amplitude of discharge potential in the pelvicalyceal pacemaker region and this was associated with a decrease in renal pelvic pressure. The frequency of the pacemaker discharge did not increase. On the other hand, in the lower pelvis and ureter, dibutyryl cyclic AMP caused a small but significant decrease in the amplitude of discharge potentials and this was associated with a marked decrease in discharge frequencies in the lower pelvis and ureter.

Effect of isoproterenol on contractile force of isolated rabbit renal pelvic smooth muscle

Isoproterenol produced a concentration-dependent increase in contractile force of rabbit upper renal pelvic smooth muscle. Conversely, isoproterenol produced a concentration-dependent decrease in contractile force of rabbit lower renal pelvic smooth muscle. These data show that in response to isoproterenol upper renal pelvic smooth muscle, which is thought to act as a pacemaker region for pelviureteral peristalsis, resembles cardic muscles, whereas lower pelvic smooth muscle is similar to ureter and other smooth muscles.

The effect of serum dilution on free thyroxine (T4) concentration in the low T4 syndrome of nonthyroidal illness

Progressive dilution of normal sera causes little change in free T4 concentrations. Similar dilution of sera containing drug inhibitors of T4 binding to serum proteins causes a progressive fall in free T4. The low T4 syndrome of nonthyroidal illness is thought to be associated with a circulating inhibitor(s) of T4 binding. It would be expected, therefore, that dilution of sera from the low T4 syndrome might also result in a fall in free T4 concentrations. We compared the effect of progressive serum dilution on free T4 concentrations in low T4 syndrome sera to those in normal, hyperthyroid, pregnancy, TBG-deficient and salicylate-containing sera. A tracer dialysis method proved inappropriate for studying dilution effects. Using a new dialysate RIA method to measure free T4, we found a progressive fall in free T4 concentrations in sera from patients with the low T4 syndrome similar to that in serum containing salicylate, but not to that in normal sera. The magnitude of the fall varied widely among individual patients. Free T4 methods which use a diluted serum sample will underestimate free T4 concentrations in the low T4 syndrome.

"On" and "off" responses of guinea pig ureter

The in vitro guinea pig ureter responds to 5-s trains of electrical stimuli with two contractions: the first, an "on" response, occurs within 0.1-0.3 s after the onset of the stimulus train; the second, an "off" response, occurs 0.2-1.0 s after the termination of the stimulus train. Force decreases between the two responses during a time when the stimulus is still being delivered. Longer duration and/or higher frequencies of stimuli within the train are required to elicit the off response than the on response. Neither the on nor the off response appears to be neurally mediated, since both responses are unchanged by tetrodotoxin, phentolamine, atropine, and pyrilamine. Decreasing temperature from 37 to 22 degrees C decreases the amplitude of the on response and increases the amplitude of the off response. Calcium-free solution, 2 mM ethylenediaminetetraacetic acid (EDTA), 1 mM Mn2+, and 1 microM verapamil abolish the on response at a time at which the off response continues to persist. Conversely, 0.5 mM caffeine and 0.1 mM theophylline abolish the off response, whereas they only slightly reduce the on response. These data suggest that the on response depends on extracellular free calcium, whereas the off response is more dependent on bound or stored calcium.

Effect of alpha adrenergic agonists and blockers on Purkinje fiber transmembrane potentials and automaticity in the dog

Previous studies have shown that alpha adrenergic stimulation can reduce the automaticity of canine Purkinje fibers. In the present study, our interest was to determine whether this is an alpha-1 or alpha-2 adrenergic action. We used standard microelectrode techniques to study the effects of the alpha agonists, phenylephrine and clonidine, and the alpha antagonists, prazosin and yohimbine, on phenylephrine-induced decreases in automaticity. Prazosin and yohimbine, 1 X 10(-5) M, alone, significantly reduced the amplitude and upstroke velocity (Vmax) of stimulated action potentials. In addition, yohimbine, 1 X 10(-5) M, accelerated and prazosin, 1 X 10(-5) M, attenuated repolarization. Prazosin, 1 X 10(-5) M, and yohimbine greater than or equal to 1 X 10(-7) M, alone, decreased automaticity. Phenylephrine, 5 X 10(-8) M, alone, significantly increased the cycle length of automatic Purkinje fibers. The effects of phenylephrine on automaticity were blocked by prazosin but not by yohimbine. Clonidine, alone, 1 X 10(-6) and 1 X 10(-5) M, significantly reduced automaticity, an effect that was not blocked by yohimbine or prazosin. Clonidine, 1 X 10(-6) and 1 X 10(-5) M, also significantly reduced Vmax and prolonged action potential duration of driven Purkinje fibers, an action consistent with direct membrane effects. These experiments suggest that the negative chronotropic effects of phenylephrine on Purkinje fiber automaticity are mediated by alpha-1 adrenergic receptors.

Force-velocity relationships of guinea pig ureter

Longitudinal force-velocity relationships of the guinea pig ureter were studied in vitro in 3 age groups: 2 to 3 weeks, 2 to 3 months and 2 to 3 years. Velocity of shortening depends on the load lifted and not on the initial length of the muscle. Force-velocity relationships did not change with age, but the isometric force when the velocity is zero and no shortening occurs, increased with age. The shortening of the muscle, expressed as per cent of in vivo length, was independent of age and of preload. Therefore, work performed by a unit length of ureter which is the product of shortening and load lifted, and power which is the product of velocity and load lifted, are unaffected by age or by initial length. Thus there appears to be no significant age-related change in isotonic parameters of contraction such as velocity, shortening, work and power.

The hydrophobic moment detects periodicity in protein hydrophobicity

Periodicities in the polar/apolar character of the amino acid sequence of a protein can be examined by assigning to each residue a numerical hydrophobicity and searching for periodicity in the resulting one-dimensional function. The strength of each periodic component is the quantity that has been termed the hydrophobic moment. When proteins of known three-dimensional structure are examined, it is found that sequences that form alpha helices tend to have, on average, a strong periodicity in the hydrophobicity of 3.6 residues, the period of the alpha helix. Similarly, many sequences that form strands of beta sheets tend to have a periodicity in their hydrophobicity of about 2.3 residues, the period typical of beta structure. Also, the few sequences known to form 3(10) helices display a periodicity of about 2.5 residues, not far from the period of 3 for an ideal 3(10) helix. This means that many protein sequences tend to form the periodic structure that maximizes their amphiphilicity. This observation suggests that the periodicity of the hydrophobicity of the protein primary structure is a factor in the formation of secondary structures. Moreover, the observation that many protein sequences tend to form segments of maximum amphiphilicity suggests that segments of secondary structure fold at a hydrophobic surface, probably formed from other parts of the folding protein.

Is renal ultrasound a reliable indicator of a nonobstructed duplication anomaly?

Twelve kidneys which had a non-obstructed duplication anomaly on excretory urography were studied sonographically. Ten of the twelve kidneys had a single central renal sinus echo complex; only two kidneys had a split sinus complex typical of duplication. Sonography is not a reliable technique to identify a nonobstructed duplication anomaly.

Actions of adenosine on normal and abnormal impulse initiation in canine ventricle

We studied the role of adenosine in modulating pacemaker activity in normal and infarcted ventricular tissues. We used standard microelectrode techniques to study the effects of adenosine on impulse initiation in Tyrode's superfused normal canine Purkinje fibers (PF), PF obtained from experimentally infarcted hearts, and BaCl2-superfused PF. Adenosine reduced automaticity of normal PF, whereas beta, gamma-methylene ATP did not. In infarcted and in Ba2+-depolarized PF, adenosine had no effect on automaticity or the action potential. We then used intracellular current injection to vary the membrane potentials of normal PF and found adenosine to depress automaticity more at high than at low membrane potentials. The ability of adenosine to counteract the effects of epinephrine on automaticity also was related to membrane potential. We conclude that adenosine depresses normal automaticity but has little effect on abnormal impulse initiation at low membrane potentials. It therefore appears that in the setting of myocardial infarction or ischemia the extent to which adenosine release will modify the function of normal and ectopic pacemakers will be influenced by the membrane potentials of those pacemakers.

Characteristics of normal and refluxing ureterovesical junctions

In order to quantitatively define the mechanism of urereterovesical junction (UVJ) competence and vesicoureteral reflux, we measured ureteral pressures using a continuously perfused catheter with a single side opening. Studies were performed under general anesthesia on 11 competent and 9 refluxing UVJs. The amplitude of ureteral contractions was essentially the same in refluxing and non-refluxing systems, but peristaltic frequency was significantly lower in the presence of even the milder forms of reflux. With the bladder empty, a high pressure zone was observed at the UVJ in both refluxing and non-refluxing systems, with no significant pressure difference between the 2 groups. No relaxation was observed during urine transport across the UVJ. With bladder filling, a greater increase in profile pressure occurred at the UVJ of non-refluxing than refluxing systems. The UVJ-bladder pressure gradient of non-refluxing systems increased with bladder filling, whereas the gradient in the refluxing systems decreased. It appears that refluxing ureters have a decreased peristaltic frequency and fail to maintain a pressure gradient at the UVJ with bladder filling.

Rationale for ureteral tapering

With two to three weeks of obstruction, marked ureteral dilatation develops in the presence of relatively low intraluminal pressures. The low pressure and increasing dimensions primarily reflect alterations in intrarenal hemodynamics and the viscoelasticity of the ureteral wall, respectively. Associated with these changes, the ureteral muscle hypertrophies, and this is accompanied by an increase ability to contract, as evidenced by an increase in contractile force and stress. Despite muscle hypertrophy and increased contractility, the dilated ureter is less able to generate the contractile intraluminal pressure waves that are required for urine transport. This paradoxical decrease in intraluminal pressure with increasing contractile force and diameter is explained by the Laplace relationship which also provides a rationale for ureteral tapering. Ureteral tapering by decreasing diameter allows the obstructed ureter's ability to generate contractile forces to be translated into higher contractile intraluminal pressures which provide for more efficient urine transport.

The helical hydrophobic moment: a measure of the amphiphilicity of a helix

The spatial distribution of the hydrophobic side chains in globular proteins is of considerable interest. It was recognized previously that most of the alpha-helices of myoglobin and haemoglobin are amphiphilic; that is, one surface of each helix projects mainly hydrophilic side chains, while the opposite surface projects mainly hydrophobic side chains. To quantify the amphiphilicity of a helix, here we define the mean helical hydrophobic moment, (mu H) = [sigma Ni = 1Hi]/N, to be the mean vector sum of the hydrophobicities Hi of the side chains of a helix of N residues. The length of a vector Hi is the signed numerical hydrophobicity associated with the type of side chain, and its direction is determined by the orientation of the side chain about the helix axis. A large value of (mu H) means that the helix is amphiphilic perpendicular to its axis. We have classified alpha-helices by plotting their mean helical moment versus the mean hydrophobicity of their residues, and report that transmembrane helices, helices from globular proteins and helices which are believed to seek surfaces between aqueous and nonpolar phases, cluster in different regions of such a plot. We suggest that this classification may be useful in identifying helical regions of proteins which bind to the surface of biological membranes. The concept of the hydrophobic moment can be generalized also to non-helical protein structures.