Dynamic relationships of trabecular bone density, architecture, and strength in a computational model of osteopenia.

A computational model was developed to study the effects of short- and long-term periods of disuse osteopenia and repair to elucidate the interrelationships between bone mass, architecture, and strength. The model is one in which the sequence of structural change events is followed in time. This temporal feature contrasts with studies of real trabecular tissue which are necessarily cross-sectional in nature and do not lend themselves to insights into the dynamic nature of the structural changes with time. In the model it was assumed that the stimulus for bone adaptation to mechanical load is the local mechanical strain rate, according to which the trabecular surfaces are differentially formed and resorbed. The effects of mechanical loading and unloading (disuse) on the cancelous bone properties were studied. The bone mass, architecture, and elastic stiffness were shown to be strongly dependent upon the period of the unloading phase, as well as the period of the reloading phase. Mechanical stiffness is demonstrated computationally to be a multivalued function of bone mass, if architecture is not accounted for. The model shows how the same value of trabecular bone mass can be associated with two or more distinct values of biomechanical stiffness. This result is the first explicit demonstration of how bone mass, architecture, and strength are related under dynamical load-bearing conditions. The results explain the empirical observation that bone mass can account for about 65% of the observed variation in bone strength, but that by incorporating measures of bony architecture into the analysis, the predictability is increased to 94%. The computational model may be used to explore the effects of different loading regimes on mass, architecture, and strength, and potentially for assistance in designing both animal and clinical bone loss studies.

Microelectrometric titration measurement of the pKa's and partition and drug distribution coefficients of narcotics and narcotic antagonists and their pH and temperature dependence.

The pKa's, partition coefficients, and drug distribution coefficients (apparent partition coefficients) have been investigated for a number of narcotics and, where possible, for their congener narcotic antagonists. These studies were carried out by a microelectrometric titration technique as a function of temperature and pH. This method enables one to determine not only the dissociation constants to deconvolute overlapping pKa's, but also to determine the solubilities of oil-water distribution of these various drugs. The drug distribution coefficients displayed marked sensitivity to pH at values which span the range of attainable human physiological pH values. This has significant pharmacological implications for proper choice and scaling of drug dosages under various clinical situations. The partition coefficients and drug distribution coefficients were noticeably different at 20 degrees (where such measurements are customarily made) than at 37 degrees (body temperature). Furthermore, various drugs exhibit very nonequivalent increases in drug distribution coefficients with increasing temperature, ranginf from 21% for morephine to 200% for naltrexone. This nonregularity indicates that it will not be valid to extrapolate by any constant factor the measurements made at lower temperatures. Even the true partition coefficients increase with temperature from 20 degrees to 37 degrees. There is more of a difference in the drug distribution coefficients for naloxone and naltrexone than might have been expected from the similarities in their structures with naltrexone being significantly less lipophilic than naloxone. This would imply that this would lead to naloxone having a more rapid onset for antagonist activity and likewise a shorter duration of action than naltrexone.

The effect of verapamil in reducing the severity of acute tubular necrosis in canine renal autotransplants.

Calcium channel blockade has been shown to prevent warm renal ischemic damage. The ability of verapamil to decrease the severity of acute tubular necrosis (ATN) after 24-hr cold storage and autotransplantation was studied in a randomized paired study of 12 dogs. Experimental animals pretreated with intraarterial verapamil and flushing of the harvested kidney with cold intracellular solution containing verapamil demonstrated significantly (P less than .05) greater renal function preservation over their matched controls. A subsequent nonpaired study of 6 dogs treated only with flushing of the harvested kidney with perfusate containing verapamil demonstrated no significant preservation advantage over controls. We conclude that verapamil, administered prior to the ischemic event, can enhance the protective effect of hypothermia and decrease the severity of ATN in ischemically injured kidneys.

Passive urethral compression with a silicone gel prosthesis for the treatment of male urinary incontinence.

Eighty-six patients who underwent implantation of the silicone gel prosthesis for post-prostatectomy incontinence are the subject of this study. The operation entails the implantation of a silicone gel prosthesis in the perineum to provide passive urethral compression. Several modifications of this operation have been implemented in the last 2 years, and analysis of our results indicates that lasting benefit can be achieved in about 70% of patients.

Ureteral injury from ureteroscopic stone manipulation.

A ureteroscopy for stone removal resulted in a tear of the ureter and extensive necrosis requiring ureteroneocystostomy. Urologists are urged to report complications of upper tract endoscopy and to apprise patients of the inherent dangers.

"O" ring urinary ostomy appliance.

A non-adhesive urostomy system represents a major departure from ostomy appliances that have been used to date. Experience of 123 ostomates who have lived with the traditional as well as the new appliance indicates a high degree of patient acceptance and satisfaction. The "O" ring appliance promises to simplify and improve the quality of life for patients who are committed to this form of urinary disposition.

Leiomyosarcoma of renal vein and inferior vena cava.

A case of leiomyosarcoma of the right renal vein and inferior vena cava causing total obstruction of the vena cava is reported. This rare condition was treated successfully after two previous operations had deemed it unresectable. Treatment consisted of a right nephrectomy and resection of the vena cava and ligation of the left renal vein. Because of the slow growth of the well-differentiated leiomyosarcoma, there was no problem with venous return from the left kidney, and the patient recovered promptly without evidence of renal function impairment. Postoperatively, she received chemotherapy consisting of doxorubicin (Adriamycin) and vincristine. She is well and free of tumor over four years postoperatively. The good result, in this case, is attributed to complete surgical excision and multimodal therapy.

Primary carcinoid tumor of testis with metastasis.

A primary carcinoid tumor of the testis metastatic to one preaortic lymph node in a forty-three-year-old man is reported. The case was of great clinical interest not only because of the extreme rarity of testicular carcinoid with metastasis but also because of a coincidental bacterial endocarditis.

Silicone-gel prosthesis in treatment of urinary incontinence secondary to neurogenic bladder dysfunction.

Patients with lower neuron lesion neurogenic bladder, with normal upper urinary tracts, poor closing pressure of the urethra, and absence of vesicoureteral reflux can be considered candidates for the insertion of the silicone-gel (Kaufman) prosthesis. Our results in 10 cases indicated that there is a place for passive urethral compression in the treatment of neurogenic bladder after a careful selection of patients and using objective methods to regulate the amount of urethral compression. The use of a combined operation (silicone-gel prosthesis and a Small-Carrion prosthesis) in some of the cases is also presented.

Why Marshall-Marchetti operation works . . . or does not.

Vesicourethral suspension operations fail (1) when preoperative evaluation is insuffcient, leading to improper selection of patients; and (2) for technical reasons when anatomy is uncorrected (suture malplacement, suture breakage, and failure to release adhesions) or when anatomy is corrected (periurethral fibrosis, fistula, stone or granuloma formation on nonabsorbable suture, and overcorrection). Vesicourethral suspension operations work by changing urethrotrigonal anatomy, creating a new equilibrium of forces acting on the bladder neck and urethra.

External velour dacron grafts in renal artery reconstruction.

Aortorenal interposition grafts were performed in dogs using a new external velour knitted Dacron graft. Encapsulation and endothelialization of these grafts occurs as early as two weeks postoperatively. Complete healing is seen by six weeks, and the cellular lining of these grafts appears to be continuous with, and histologically similar to, the endothelium of contiguous arteries. The healed nonthrombogenic characteristics of this graft material represents a considerable improvement over graft materials of conventional design.

Renal preservation with inosine.

Isosine improved post-transplantation function of canine kidneys subjected to thirty minutes of normothermic ischemia followed by flushing and twenty-four-hour cold storage. Inosine was not able to improve renal preservation when cold storage was extended to forty-eight hours after thirty minutes of normothermic ischemia.

Successful use of transureteroureterostomy to salvage ureterosigmoidostomy after anastomotic failure.

Four cases are presented of patients who had undergone ureterosigmoidostomy and in whom a unilateral ureteral anastomotic complication developed that was salvaged subsequently by a transureteroureterostomy. Although other forms of urinary diversion are now being utilized routinely in many centers, the ureterosigmoidostomy is still being employed worldwide, and urologic surgeons need to be versed in its potential problems and how to correct them.

Aspiration biopsy of prostate.

Needle biopsy of the prostate has been widely practiced for more than twenty-five years, whereas transrectal aspiration biopsy, first described fifty years ago, has not. We describe our experience using the transrectal aspiration biopsy and correlate the results with histologic studies of the prostate obtained by conventional needle biopsy and surgical specimens. Aspiration needle biopsy of the prostate has a high degree of diagnostic accuracy, it causes minimal inconvenience and discomfort, the results are rapidly available, the ease of entering the suspected area in the prostate is more precise than with conventional needle biopsy, and sampling of prostate can be greater. The disadvantages of aspiration biopsy are that the technique, being unfamiliar to most urologists, must be learned and requires an experienced cytologist for interpretation. Cytologic evaluation by aspiration biopsy and the histologic diagnosis by conventional needle biopsy are complementary.

Methyldopa in treatment of neurogenic bladder disorders.

Fifty patients with neurogenic bladder dysfunction were treated with methyldopa (Aldomet). The preliminary results that are presented suggest a beneficial action in patients with upper neuron lesions. The probable mechanism of the drug's action is discussed.

Use of saralasin to detect renovascular hypertension in childhood.

Current methods to evaluate renovascular hypertension in the pediatric population often requires a general anesthetic. Saralasin, an angiotensin II competitive inhibitor, is a safe, noninvasive technique which can be utilized at the bedside in a salt-depleted child off antihypertensive medication. Two illustrative cases are presented.

Effects of preliminary normothermic flushing on hypothermic renal preservation.

Flushing of harvested kidneys with hypothermic perfusates is presumed to cause inappropriate circulation due to vasospasm. Effects of initial normothermic flushing prior to hypothermic flushing and cold preservation were tested in canine kidneys. Analysis of the perfusion characteristics revealed that a brief initial flushing with solutions at 37 degrees C. eliminates vasoconstriction and even facilitates subsequent hypothermic flushing. In amounts not exceeding 100 cc. it was not deleterious to transplant function. Larger volumes of normothermic flushing were proved to cause endothelial injury and resulted in poor transplant survival.

Result of treatment of patients with stage D1 prostatic carcinoma.

Between 1972 and 1982, 59 patients who had documented pelvic lymph node metastases, proved by pelvic lymphadenectomy, were available for analysis. Radical retropubic prostatectomy was the primary treatment in 33 patients with or without other therapies, while 23 patients received external beam radiation therapy as their primary treatment. Three patients received hormonal therapy alone. Forty-two of 59 patients are alive for a crude survival of 71 per cent. Sixteen patients have died of metastases. Patients with low-grade tumors, small tumor burden, and limited lymph node metastases had excellent short-term survival after radical prostatectomy.

Urethral gap in complete disruption of membranous urethra.

In patients with complete disruption of the membranous urethra treated initially with placement of a suprapubic cystostomy, delayed synchronous retrograde and voiding cystourethrograms failed to demonstrate accurately the distance between the two urethral ends. Radiographic exposure obtained during synchronous instrumentation of the anterior and posterior urethra in the anesthetized patient was the most precise method of defining the extent of the urethral gap. Any surgical decision should be based on this type of investigation. In most cases of pelvic crush injuries, the severed membranous urethra probably remains attached in close proximity to the distal segment, thus directing the redescent of the prostate and bladder base in the presence of a contracting pelvic hematoma.