Ureteral reconstruction: small intestine submucosa for the management of strictures and defects of the upper third of the ureter

PURPOSE

We evaluated the effectiveness of small intestine submucosa in ureteral reconstruction.

MATERIALS AND METHODS

We report an experimental study in 6 female pigs weighing between 50 and 60 pounds. The animals were anesthetized, midline laparotomy was performed and two-thirds of the diameter of the upper third of the left ureter were incised parallel to the ureteral axis, leaving intact only a third of the ureteral wall for a segment of 7 cm. A 5Fr double-J*; stent was positioned to secure patency at all times. The created gap was then bridged with an small intestine submucosa patch in a cylindrical format, which was subsequently sutured to the proximal and distal ureteral segment. The right ureter served as our control and simple intubated Davis ureterotomy was performed.

RESULTS

All animals survived the whole followup of 7 weeks. Histologically there was evidence of epithelial regeneration along the segments reconstructed with small intestine submucosa, supported by a well vascularized collagen and smooth muscle background. There was no evidence of foreign body reaction to the graft material. In vivo patency was confirmed by retrograde pyelography in the bridged ureters 7 weeks after the initial procedure. All the ureters without an small intestine submucosa bridge had ureteral stenosis without evidence of epithelial regeneration.

CONCLUSIONS

The use of small intestine submucosa is a novel, effective material for the scaffolding of ureteral defects and/or strictures of the upper ureteral segment in the pig model.

A report of intracranial Rosai-Dorfman disease with literature review

Rosai-Dorfman disease (sinus histiocytosis with massive lymphadenopathy), is a rare benign histiocytic proliferative disorder. Over 650 cases have been reported since 1969. To the best of our knowledge, there have been only 31 cases with central nervous system involvement reported in the literature. Intracranial disease usually presents clinically and radiologically as a "meningioma". It can be misdiagnosed as a nonspecific inflammatory process because of the atypical histologic features of Rosai-Dorfman disease occurring in a non-nodal location. Familiarity with such atypical histologic features and appropriate use of immunohistochemical stains is required for a definitive diagnosis of central nervous system Rosai-Dorfman disease. We report such an intracranial lesion with other extranodal sites of involvement with a 5-year follow up and a review of previously reported cases. Ann Diagn Pathol 5:96-102, 2001.

Laparoscopic ureteral reconstruction with small intestinal submucosa

PURPOSE

To evaluate the feasibility of laparoscopic ureteral reconstruction with small intestinal submucosa (SIS) in the pig ureter.

MATERIALS AND METHODS

Eight female pigs weighing between 25 and 30 kg were enrolled. After anesthesia was administered, a double-pigtail stent was inserted, the animals were moved to a lateral decubitus position, pneumoperitoneum was established, and three 10-mm ports were positioned. The ureter was opened longitudinally for 7 cm, and two thirds of the periphery of the upper third of the left ureter was excised. The SIS was anastomosed to the upper and distal ureteral segments with chromic 4-0 sutures. The double-pigtail stent was removed 6 weeks after the initial procedure, and retrograde pyelography was performed a week later to confirm the viability of the pelvicaliceal system.

RESULTS

The average duration of the procedures was 210 minutes (range 125-250 minutes). All animals survived the entire follow-up period of 7 weeks. Retrograde pyelography revealed a patent ureteral lumen, and no obstructive phenomena were observed. Histologically, the SIS-regenerated ureteral segments were remarkably similar to normal porcine ureters and were indistinguishable from neighboring tissue.

CONCLUSION

Laparoscopic ureteral reconstruction with SIS proved to be effective and technically feasible. The SIS seems to be an effective biodegradable scaffold, facilitating regeneration of host tissue.

The A-type potassium channel Kv4.2 is a substrate for the mitogen-activated protein kinase ERK

The mitogen-activated protein kinase ERK has recently become a focus of studies of synaptic plasticity and learning and memory. Due to the prominent role of potassium channels in regulating the electrical properties of membranes, modulation of these channels by ERK could play an important role in mediating learning-related synaptic plasticity in the CNS. Kv4.2 is a Shal-type potassium channel that passes an A-type current and is localized to dendrites and cell bodies in the hippocampus. The sequence of Kv4.2 contains several consensus sites for ERK phosphorylation. In the present studies, we tested the hypothesis that Kv4.2 is an ERK substrate. We determined that the Kv4.2 C-terminal cytoplasmic domain is an effective ERK2 substrate, and that it is phosphorylated at three sites: Thr(602), Thr(607), and Ser(616). We used this information to develop antibodies that recognize Kv4.2 phosphorylated by ERK2. One of our phospho-site-selective antibodies was generated using a triply phosphorylated peptide as the antigen. We determined that this antibody recognizes ERK-phosphorylated Kv4.2 in COS-7 cells transfected with Kv4.2 and native ERK-phosphorylated Kv4.2 in the rat hippocampus. These observations indicate that Kv4.2 is a substrate for ERK in vitro and in vivo, and suggest that ERK may regulate potassium-channel function by direct phosphorylation of the pore-forming alpha subunit.

Chronic expansion of the renal pelvis: a new method for reconstruction of upper ureteral defects

OBJECTIVES

To evaluate whether the dilated renal pelvis can be used as an autologous source for the surgical reconstruction of upper ureteral defects or strictures.

METHODS

In 7 female pigs, the renal pelvis was expanded by a percutaneously placed Council balloon catheter. Every other day for 4 weeks, the renal pelvis was progressively dilated with a bolus injection of saline and contrast medium, which allowed expansion of the renal pelvis to 70 to 75 mL. Four to six weeks after the initial intervention, 5 to 7 cm of the proximal ureter was resected in an open operation and replaced with a tubularized spiral flap made from the expanded renal pelvis. Three weeks later, the animals were killed, and the area of manipulation was resected for pathologic evaluation.

RESULTS

All animals reached the desired expansion of the renal pelvis, and in all cases, the spiral flap was fashioned and anastomosed to the distal ureteral segment, bridging the initial defect (mean length 7 cm). Two animals died from sepsis, 4 and 6 days after the spiral flap reconstruction. A viable ureteral lumen with a patent anastomosis and a functioning pelvocaliceal unit was observed on intravenous urography in all animals. The main histologic findings were a chronic inflammatory process with concomitant mucinous metaplasia and reactive atypia of the tubules.

CONCLUSIONS

The use of a balloon expander in the renal pelvis is a safe and effective technique for producing native tissue for the reconstruction of defects or strictures of the upper ureteral segment.

Input-specific immunolocalization of differentially phosphorylated Kv4.2 in the mouse brain

Voltage-gated A-type potassium channels such as Kv4.2 regulate generation of action potentials and are localized abundantly in the hippocampus and striatum. Phosphorylation consensus sites for various kinases exist within the sequence of the potassium channel subunit Kv4.2, including consensus sites for extracellular signal-regulated kinase/mitogen activated protein kinase (ERK/MAPK), protein kinase A (PKA), protein kinase C (PKC), and calcium/calmodulin-dependent kinase II (CaMKII), and kinase assays have shown that particular amino acids of the consensus sites are bonafide phosphorylation sites in vitro. We have developed antibodies recognizing Kv4.2 triply phosphorylated at the three ERK sites as well as two antibodies recognizing singly phosphorylated Kv4.2 channels at the PKA sites (one amino-terminal and one carboxy-terminal). In the present study, we report the development of reliable immunohistochemistry protocols to study the localization of these phosphorylated versions of Kv4.2, as well as total Kv4.2 in the mouse brain. A general description of the areas highlighted by these antibodies includes the hippocampus, amygdala, cortex, and cerebellum. Such areas display robust synaptic plasticity and have been implicated in spatial, associative, and motor learning. Interestingly, in the hippocampus, the antibodies to differentially phosphorylated Kv4.2 channels localize to specific afferent pathways, indicating that the Kv4.2 phosphorylation state may be input specific. For example, the stratum lacunosum moleculare, which receives inputs from the entorhinal cortex via the perforant pathway, displays relatively little ERK-phosphorylated Kv4.2 or PKA carboxy-terminal-phosphorylated Kv4.2. However, this same layer is highlighted by antibodies that recognize Kv4.2 that has been phosphorylated by PKA at the amino terminus. Similarly, of the three antibodies tested, the soma of CA3 neurons are primarily recognized by the ERK triply phosphorylated Kv4.2 antibody, and the mossy fiber inputs to CA3 are primarily recognized by the carboxy-terminal PKA-phosphorylated Kv4.2. This differential phosphorylation is particularly interesting in two contexts. First, phosphorylation may be serving as a mechanism for targeting. For example, the amino-terminal PKA phosphorylation may be acting as a tag for a discrete pool of Kv4.2 to enter stratum lacunosum moleculare. Second, as phosphorylation may regulate channel biophysical properties, differential phosphorylation of Kv4.2 in the dendrites of pyramidal neurons may confer unique biophysical properties upon particular dendritic input layers.

Kv4.2 phosphorylation by cyclic AMP-dependent protein kinase

Recent evidence suggests that K(+) channels composed of Kv4.2 alpha-subunits underlie a transient current in hippocampal CA1 neurons and ventricular myocytes, and activation of the cAMP second messenger cascade has been shown to modulate this transient current. We determined if Kv4.2 alpha-subunits were directly phosphorylated by cAMP-dependent protein kinase (PKA). The intracellular domains of the amino and carboxyl termini of Kv4.2 were expressed as glutathione S-transferase fusion protein constructs; we observed that both of these fusion proteins were substrates for PKA in vitro. By using phosphopeptide mapping and amino acid sequencing, we identified PKA phosphorylation sites on the amino- and carboxyl-terminal fusion proteins corresponding to Thr(38) and Ser(552), respectively, within the Kv4.2 sequence. Kinetic characterization of the PKA sites demonstrated phosphorylation kinetics comparable to Kemptide. To evaluate PKA site phosphorylation in situ, phospho-selective antisera for each of the sites were generated. By using COS-7 cells expressing an EGFP-Kv4.2 fusion protein, we observed that stimulation of the endogenous PKA cascade resulted in an increase in phosphorylation of Thr(38) and Ser(552) within Kv4.2 in the intact cell. We also observed modulation of PKA phosphorylation at these sites within Kv4.2 in hippocampal area CA1. These results provide insight into likely sites of regulation of Kv4.2 by PKA.

Insights into the tetanus toxin model of early-onset epilepsy from long-term video monitoring during anticonvulsant therapy

Video monitoring studies were undertaken to determine if the anticonvulsant, carbamazepine (CBZ), could prevent seizures in infant rats that had been intrahippocampally injected with tetanus toxin (TNTX). In control rats, seizure frequency peaked 5-6 days after injection and rapidly declined by postinjection day 9. Twice-daily CBZ treatments dramatically suppressed behavioral seizures for 7 days. However, despite increasing the dosage of CBZ, rats experienced more behavioral seizures during the second week after TNTX injection. Paradoxically, tetanus-toxin-injected control rats had very few seizures at this time. Results not only suggest that this TNTX model may be useful in screening drugs for treating intractable focal epilepsy of infancy but also provide some insight into the processes that may contribute to the rapid decline in behavioral seizure frequency that occurs during the acute phase of epileptogenesis in this model.

Ibuprofen combined with antibiotics suppresses renal scarring due to ascending pyelonephritis in rats

PURPOSE

In acute pyelonephritis renal scarring may be decreased by immediate antibiotic therapy. Unfortunately in children there is often a delay in starting treatment, which increases the likelihood of renal scarring. In rodents immediate antibiotic therapy is effective for preventing renal scar formation resulting from experimentally induced pyelonephritis. However, the same treatment beginning 72 hours after infection does not prevent renal scarring in this paradigm. We examined whether delayed administration of the nonsteroidal anti-inflammatory agent ibuprofen only or combined with antibiotics suppresses renal scarring in a model of ascending pyelonephritis in rats.

MATERIALS AND METHODS

An inoculum of 5x10(9) organisms per ml. of Escherichia coli strain BH-5 was instilled into the bladder of rats and the urethra was occluded for 4 hours. Groups of animals were and were not treated with 15 mg./kg. cefadroxil or 10 mg./kg. ibuprofen given twice daily for 5 days, or the 2 drugs combined. Treatment began 72 hours after inoculation. In an additional group of rats sterile phosphate buffered saline was instilled into the bladder. In each rat the kidneys were examined grossly and microscopically 6 weeks later.

RESULTS

Combined antibiotics and ibuprofen significantly inhibited gross renal scarring compared with no treatment or antibiotics only (p<0.05). No difference in renal scarring was detected in animals that received no treatment versus those that received antibiotics or ibuprofen only (p>0.05).

CONCLUSIONS

Renal scarring resulting from acute pyelonephritis in this rat model is not decreased by delayed treatment with antibiotics only. The addition of ibuprofen to antibiotic therapy is effective for decreasing renal scarring due to acute pyelonephritis even when treatment is delayed for 72 hours.

A chronic focal epilepsy with mossy fiber sprouting follows recurrent seizures induced by intrahippocampal tetanus toxin injection in infant rats

Studies were conducted to characterize a chronic epileptic condition that follows recurrent seizures induced by intrahippocampal tetanus toxin injection in infancy. Wistar rat pups received a single injection of tetanus toxin in the right CA3 region on postnatal day 10. Animals were monitored for epileptiform activity by video electroencephalographic or visual observation during the following three to five days. Repeat evaluation six months later demonstrated interictal discharges in 79% (11 of 14) and electrographic seizures in 42% (six of 14) of adult rats with tetanus toxin-induced seizures in infancy. Five of the animals had interictal activity which occurred focally in either the left (n = 2) or right (n = 3) hippocampus. One animal had focal interictal activity independently in these regions and in the left and right cortical regions. The remaining five animals had interictal activity in the hippocampus and synchronously in the ipsilateral cortex or the contralateral hippocampus. Electrographic seizures were focal (nine of 14) or bilateral (five of 14) in onset. The behaviors that accompanied these seizures were quite variable. Clonic face and forelimb movements were observed in some animals. However, a significant portion of rats had electrographic seizures with no associated behavioral change. Timm staining was performed on hippocampal sections from experimental and control animals. There was a significantly greater Timm score (aberrant Timm granules) in the inner molecular layer of the dentate gyrus in tetanus toxin-treated rats than in control rats. Our findings suggest that intrahippocampal tetanus toxin injection in infant rats results in a chronic focal epilepsy that persists for at least six months and is associated with aberrant mossy fiber sprouting in the dentate gyrus. The model described here contributes significantly to the evidence for chronic effects of recurrent seizures in early life, and provides a model for investigation of the molecular and cellular events that contribute to the development of chronic epilepsy.

Failed endopyelotomy: low expression of TGF beta regardless of the presence or absence of crossing vessels

BACKGROUND AND OBJECTIVE

Endopyelotomy relies on Davis' intubated ureterotomy principle of healing by secondary intention and smooth-muscle regeneration. Approximately 15% of endopyelotomies fail, and the restrictured segment almost always shows evidence of reactive fibrosis with little smooth-muscle regeneration. Previous data suggests that an elevation of TGF beta in obstructed ureteropelvic junctures may be necessary for successful tissue repair following endopyelotomy. The role of crossing vessels in endopyelotomy failure is very controversial. To better understand the pathophysiology of endopyelotomy failure, the expression of transforming growth factor-beta (TBG beta) in patients with a failed endopyelotomy and crossing vessels was compared with that in patients without crossing vessels, as well as those having primary pyeloplasty or a normal ureteropelvic junction (UPJ).

MATERIALS AND METHODS

The expression of TGF beta was detected immunohistochemically in slide-mounted thin sections (4 microns) cut from paraffin-blocked adult UPJ segments obtained during primary pyeloplasty (N = 11), secondary pyeloplasty after failed endopyelotomy with documented crossing vessels (N = 10), secondary pyeloplasty after failed endopyelotomy without crossing vessels (N = 11), and normal UPJs removed during nephrectomy for purposes unrelated to obstruction (N = 11). Expression was graded on a scale of 0 to 4.

RESULTS

The combined failed endopyelotomy group had a significantly (P < 0.05) lower level of TGF beta (1.9 +/- 0.7) than did primary obstructed UPJs (2.6 +/- 0.7). The TGF beta level in the crossing vessels group (1.9 +/- 0.7) did not differ from that in the group without crossing vessels (1.8 +/- 0.7), nor did it differ from that in the group with normal UPJs (1.6 +/- 0.7). As expected, primary obstructed UPJs had a significantly higher level of TGF beta than normal ones (P < 0.02).

CONCLUSIONS

Obstructed UPJs that had failed endopyelotomy had a similarly reduced level of TGF beta whether or not crossing vessels were present. These data suggest that an elevation of TGF beta in obstructed UPJs may be necessary for successful tissue repair after endopyelotomy and that the presence of crossing vessels is probably not relevant.

Endopyelotomy failure is associated with reduced transforming growth factor-beta

PURPOSE

Approximately 15% of patients with ureteropelvic junction obstruction have endopyelotomy failure and require an additional surgical procedure to remove the obstruction. Transforming growth factor-beta (TGF-beta), a cytokine which stimulates mesenchymal cell proliferation and extracellular matrix deposition, increases in the renal pelvis in response to obstruction. However, TGF-beta also is implicated in smooth muscle regeneration and wound healing. To understand the pathophysiology of ureteropelvic junction obstruction and determine why endopyelotomy fails in some obstructed ureteropelvic junctions, TGF-beta expression in obstructed and normal ureteropelvic junction segments was compared.

MATERIALS AND METHODS

Immunohistochemical staining using a rabbit polyclonal anti-TGF-beta was performed on deparafinfized 4 microm. sections of paraffin blocked ureteropelvic junction segments. Human obstructed ureteropelvic junction segments were removed during primary pyeloplasties (11) and secondary pyeloplasties after endopyelotomy failure (11). Normal ureteropelvic junction segments were removed during nephrectomy for purposes unrelated to obstruction (11). Grading on a scale of 0 to 4 was performed by a physician blinded to the source of the specimen.

RESULTS

Mean TGF-beta expression plus or minus standard error of the mean was significantly increased (p <0.02) in obstructed ureteropelvic junctions from primary pyeloplasties (2.6+/-0.7) compared to normal ureteropelvic junctions (1.6+/-0.7), as expected. However, TGF-beta expression in the endopyelotomy failure group (1.8+/-0.6) was not significantly different from that in normal ureteropelvic junctions and was significantly lower (p <0.05) than that in obstructed ureteropelvic junctions from primary pyeloplasties.

CONCLUSIONS

Obstructed ureteropelvic junctions in cases of endopyelotomy failure have decreased expression of TGF-beta compared with other obstructed ureteropelvic junctions. These data suggest that an elevation of TGF-beta in obstructed ureteropelvic junctions may be necessary for successful tissue repair after endopyelotomy.

Necrosis of the urethra and tissue sloughing: a delayed complication after transurethral microwave thermotherapy

Transurethral microwave thermotherapy is a minimally invasive treatment for benign prostatic hyperplasia designed to destroy hyperplastic tissue without damaging the urethra. We present an unexpected complication of prostatic urethral necrosis and tissue sloughing after thermotherapy and discuss its possible cause.

Blind-ending ureteral duplication: cause of asymptomatic abdominal mass

Blind-ending ureteral duplication is a rare anomaly. The authors report on a 5-year-old girl who presented with an asymptomatic abdominal mass in which computerized axial tomography was used to make the diagnosis. The embryology of this anomaly is reviewed.

Increased susceptibility to tetanus toxin-induced seizures in immature rats

Studies were undertaken to compare tetanus toxin-induced electrographic and behavioral seizure activity in immature and adult rats. Multifocal epileptiform activity was induced by unilateral hippocampal injection of tetanus toxin in 10-day-old immature and in 90-120-day-old adult rats. Bilateral cortical surface electrodes and, in some animals, hippocampal depth electrodes were placed and serial video EEG was recorded for 2 h during the week following tetanus toxin injection. Tetanus toxin-induced interictal spike frequency was significantly higher and seizure duration was significantly longer in immature compared to adult rats. Immature rats tended to have more frequent seizures compared with adults, but the difference was not statistically significant. Ictal behaviors were different for the two groups with immature rats commonly demonstrating wild running seizures which were not seen in adult rats. These findings suggest that there are age-dependent differences in electrographic and behavioral seizure expression in the tetanus toxin seizure model and that the epileptic syndrome in immature rats is more severe.

Severity of medical and neurologic complications as a determinant of neurodevelopmental outcome at 6 and 12 months in very low birth weight infants

Very low birth weight (n = 154) and term infants (n = 119) had neurologic and developmental assessment at 6 and 12 months of age. Preterm infants with severe neonatal complications were considered to be at high risk, and those with milder complications were considered to be at low risk, for neurodevelopmental abnormality. Compared to term infants, high- and low-risk infants had abnormalities at 6 months in total neurologic score, cranial nerves, motor tone, motor coordination, and reflexes (P < .001). At 12 months, all groups had improved. However, high-risk infants had persistent abnormalities in the same subcategories (P < .001), whereas low-risk infants differed from term infants only in motor tone (P < .001). Bayley developmental scores were different for all groups at 6 months (P < .001), but at 12 months only high-risk infants differed from term infants (P < .01). These results demonstrate improvement in neurologic and developmental scores over time in very low birth weight infants. The degree of neurodevelopmental abnormality and improvement over time is related to severity of neonatal complications in preterm infants.

A model of bladder tumor xenografts in the nude rat

PURPOSE

An in vivo tumor model for the study of human urothelial carcinoma is desirable. Orthotopic xenografts are useful in order to better approximate human tumor cell behavior in situ. A prior model has been described in the nude mouse. However, its small bladder size limits both histologic characterization and the application of intravesical therapeutics. In the absence of preirradiation, orthotopic xenografts of human transitional cell carcinoma in the nude rat has not been previously reported.

MATERIALS AND METHODS

Nude rats 2 to 4 weeks of age were inoculated with 1-5 x 10(6) cells of RT4 (well differentiated papillary human bladder tumor cell line). Inoculation was performed via open cystotomy. Techniques of mucosal injury including acid treatment and cautery were explored in an effort to optimize tumor implantation and growth. Animals were sacrificed at varying intervals and histologic assessment was performed.

RESULTS

The overall rate of tumor implantation and growth was 93.4% (57 of 61). Tumors reliably grew within the muscularis and mucosal growth was seen as well. Intramuscular tumor growth was less differentiated and had a higher fraction of mitotic cells than mucosal tumor. Tumor growth was consistently seen as early as 2 weeks after inoculation which facilitates experimental trials. Distant metastasis was not observed. Mucosal injury did not increase the rate of tumor implantation.

CONCLUSION

This model is highly reproducible and will prove useful in the further study of bladder cancer progression as well as in the development of therapeutic modalities for both superficial and muscle invasive bladder carcinoma.

Model of human transitional cell carcinoma: tumor xenografts in upper urinary tract of nude rat

An in vivo model for the study of human transitional cell carcinoma (TCC) in the urinary tract is desirable. Orthotopic xenografts are useful in order to approximate better the behavior of human tumor cells in situ. Prior models have been described in the urinary bladder of the nude mouse and rat. We have developed the first model of implantation of human TCC in the upper urinary tract of an experimental animal. The kidneys of homozygous nude rats 4 weeks of age were inoculated with 1-5 x 10(6) cells of the RT4 well-differentiated papillary human TCC line through bilateral flank incisions, with transparenchymal injection of tumor cells into either the collecting system (renal pelvis) or the parenchyma. The overall implantation rate was 92% (54/59 kidneys). However, implantation into the collecting system occurred in only 45% (18/45) of the group. Ligation of the ureter prior to inoculation to produce urine stasis improved the mucosal implantation rate. Despite suspect urine cytology findings in the renal pelvis injection group, no distal seeding of the urinary tract was seen. Intraparenchymal tumor growth was less differentiated and had a higher fraction of mitotic cells than mucosal tumors. Vascular and lymphatic invasion were commonly seen; however, distant metastasis was not observed. This model will prove useful in determining the role of seeding in recurrent disease and in developing less invasive modalities for the treatment of upper tract TCC.

An unusual case of coccidioidomycosis

Dissemination of coccidioidomycosis is rare. The skin, musculoskeletal system, and central nervous system have been described as the most common sites of extrapulmonary disease. We present a case of an asymptomatic patient in whom the diagnosis of coccidioidomycosis was made on a lymph node biopsy. The biopsy was performed because of an abnormal mammogram and physical findings suggestive of malignancy.

Ras oncogene point mutations in bladder cancer resistant to cisplatin

Bladder tumors respond to cisplatin-based chemotherapy in 68% of cases, but only 30% will have a durable response. Recent studies have suggested that ras point mutations may produce cisplatin drug resistance in cell lines. To determine the role of ras point mutations in human tumors resistant to cisplatin, we evaluated ten tumors exposed to cisplatin and eight untreated bladder tumors for ras point mutations. Using polymerase chain reaction DNA amplification and allele-specific oligo-hybridization, we found that only one of the ten treated tumors and none of the untreated tumors harbored a ras point mutation. We conclude that ras point mutations occur infrequently in untreated bladder tumors and do not appear to correlate with cisplatin drug resistance in vivo.

Antibodies and their role in interleukin-1 research

The preceding paragraphs describe several uses of specific antibodies to IL-1. Standard radioimmunoassays and ELISA procedures were developed with demonstrated utility in studies attempting to quantitate the cytokine in cell culture fluids. In part, antibody-based assays circumvent the problems associated with bioassays. Bioassays are difficult to perform, often lack specificity due to the presence of competing cytokines and are insensitive when used with complex biological fluids due to non-specific protein binding and the presence of IL-1 antagonists. Thus, bioassays have not been broadly applicable with specimens in a clinical setting. In contrast, monoclonal antibodies and polyclonal antisera have provided a means of identifying functionally important regions of the IL-1 molecule, monitoring the post-translational processing of IL-1 which may include biologically inactive moieties, and developing new assays as illustrated by cell blot procedures.