Selection, history and chemistry: the three faces of the genetic code.

The genetic code might be a historical accident that was fixed in the last common ancestor of modern organisms. 'Adaptive', 'historical' and 'chemical' arguments, however, challenge such a 'frozen accident' model. These arguments propose that the current code is somehow optimal, reflects the expansion of a more primitive code to include more amino acids, or is a consequence of direct chemical interactions between RNA and amino acids, respectively. Such models are not mutually exclusive, however. They can be reconciled by an evolutionary model whereby stereochemical interactions shaped the initial code, which subsequently expanded through biosynthetic modification of encoded amino acids and, finally, was optimized through codon reassignment. Alternatively, all three forces might have acted in concert to assign the 20 'natural' amino acids to their present positions in the genetic code.

The molecular basis of nuclear genetic code change in ciliates.

BACKGROUND: The nuclear genetic code has changed in several lineages of ciliates. These changes, UAR to glutamine and UGA to cysteine, imply that eukaryotic release factor 1 (eRF1), the protein that recognizes stop codons and terminates translation, changes specificity. Here we test whether changes in eRF1 drive genetic code evolution. RESULTS: Database sequence analysis reveals numerous genetic code alterations in ciliates, including UGA --> tryptophan in Blepharisma americanum and the distantly related Colpoda. We sequenced eRF1 from four ciliates: B. americanum, a heterotrich that independently derived the same eRF1 specificity as Euplotes, and three spirotrichs, Stylonychia lemnae, S. mytilus, and Oxytricha trifallax, that independently derived the same genetic code as Tetrahymena (UAR --> glutamine). Distantly related ciliates with similar codes show characteristic changes in eRF1. We used a sliding window analysis to test associations between changes in specific eRF1 residues and changes in the genetic code. The regions of eRF1 that display convergent substitutions are identical to those identified in a recently reported nonsense suppression mutant screen in yeast. CONCLUSIONS: Genetic code change by stop codon reassignment is surprisingly frequent in ciliates, with UGA --> tryptophan occurring twice independently. This is the first description of this code, previously found only in bacteria and mitochondria, in a eukaryotic nuclear genome. eRF1 has evolved strikingly convergently in lineages with variant genetic codes. The strong concordance with biochemical data indicates that our methodology may be generally useful for detecting molecular determinants of biochemical changes in evolution.

Abnormal responses of myeloid progenitor cells to granulocyte-macrophage colony-stimulating factor in human cyclic neutropenia.

Granulocyte-macrophage progenitors (CFU-GM) from four patients with childhood onset cyclic neutropenia demonstrated abnormal in vitro proliferative responses to purified, recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) when examined in detailed dose-response studies. Marrow aspirate specimens were obtained for these studies from cyclic neutropenia patients (both during neutropenic nadirs and during recovery phases of cycles), from leukemia patients in remission who had received myelosuppressive chemotherapy, and from healthy normal volunteers. Nucleated marrow cells were then isolated by density-gradient centrifugation and cryopreserved to permit studies of CFU-GM from patients and controls to be carried out at the same time and in replicate. Maximum clonal growth of CFU-GM from normal subjects and from individuals recovering from drug-induced myelosuppression was elicited by 20-100 pmol/liter rhGM-CSF, and the CSF concentrations that induced half-maximal responses (ED50) were between 1.0 and 3.0 pmol/liter. In contrast, maximum growth of CFU-GM from the cyclic neutropenia patients required greater than or equal to 1.0 nmol/liter rhGM-CSF and ED50's were greater than 30.0 pmol/liter. These abnormalities in the GM-CSF responsive growth of myeloid progenitors were independent of cycle time and were most apparent with the predominantly neutrophilic 7-d CFU-GM. Moreover, differences in the growth of 14-d CFU-GM could be attributed mostly if not entirely to differences in the generation of neutrophilic colonies. These findings indicate that childhood onset cyclic neutropenia is associated with an underlying disturbance in the GM-CSF responsive growth of myeloid progenitors committed to neutrophilic differentiation.

Toxicity profile of the immunomodulatory thalidomide analogue, lenalidomide: phase I clinical trial of three dosing schedules in patients with solid malignancies.

Thalidomide is an anti-angiogenic agent currently used to treat patients with malignant cachexia or multiple myeloma. Lenalidomide (CC-5013) is an immunomodulatory thalidomide analogue licensed in the United States of America (USA) for the treatment of a subtype of myelodysplastic syndrome. This two-centre, open-label phase I study evaluated dose-limiting toxicities in 55 patients with malignant solid tumours refractory to standard chemotherapies. Lenalidomide capsules were consumed once daily for 12 weeks according to one of the following three schedules: (I) 25 mg daily for the first 7 d, the daily dose increased by 25 mg each week up to a maximum daily dose of 150 mg; (II) 25mg daily for 21 d followed by a 7-d rest period, the 4-week cycle repeated for 3 cycles; (III) 10 mg daily continuously. Twenty-six patients completed the study period. Two patients experienced a grade 3 hypersensitivity rash. Four patients in cohort I and 4 patients in cohort II suffered grade 3 or 4 neutropaenia. In 2 patients with predisposing medical factors, grade 3 cardiac dysrhythmia was recorded. Grade 1 neurotoxicity was detected in 6 patients. One complete and two partial radiological responses were measured by computed tomography scanning; 8 patients had stable disease after 12 weeks of treatment. Fifteen patients remained on treatment as named patients; 1 with metastatic melanoma remains in clinical remission 3.5 years from trial entry. This study indicates the tolerability and potential clinical efficacy of lenalidomide in patients with advanced solid tumours who have previously received multi-modality treatment. Depending on the extent of myelosuppressive pre-treatment, dose schedules (II) or (III) are advocated for large-scale trials of long-term administration.

Progressive loss of phenotypic proteins in mature granulocytes before the onset of blast crisis in human chronic myelogenous leukemia.

A combined high-performance liquid chromatography-sodium dodecyl sulfate-gel electrophoresis method for the study of the phenotypic protein patterns of mature blood granulocytes was previously described. With the use of this method in the present study, the progression of human chronic myelogenous leukemia (CML) from the stable to the blast crisis stage was shown to be accompanied by a progressive decrease in the amounts of cell membrane and granule phenotypic proteins in mature granulocytes. Survival time from the initial diagnosis was significantly shorter for CML patients whose levels of granulocyte phenotypic proteins were below the normal range compared with survival time for those patients whose levels were normal or higher than normal. The data suggest that these changes in mature granulocytes serve as useful diagnostic indicators of an impending blast crisis in CML patients.

Phase I and clinical pharmacology study of intravenous flavone acetic acid (NSC 347512).

We have conducted a Phase I and pharmacological study of flavone acetic acid, one of a series of novel flavonoids. The drug was administered i.v. weekly for 4 weeks, with a 2-week rest and then repeated. Flavone acetic acid was given initially in a 1-h infusion, but at the 3900-mg/m2 dose level, the infusion time was lengthened to 3 h. A total of 31 patients were treated with 9 different dose levels, ranging from 330 to 6400 mg/m2. Dose-limiting toxicity was acute hypotension that began after about one-third of each drug dose had been infused and rarely lasted more than a few minutes after the infusion was discontinued. In addition, subjective fatigue and asthenia causing unacceptable patient discomfort was dose limiting. A significant side effect noted that was not dose limiting was diarrhea during the infusion. This drug exhibited nonlinear pharmacokinetic behavior. Plasma levels exceeded 300 micrograms/ml during the infusion at the maximally tolerated dose. After the infusion ended the principal half-life was about 2 h. In 24-h urine collections 27% of the flavone acetic acid dose was recovered as intact drug and an additional 37% was recovered as a metabolite. The maximally tolerated dose determined in this study is 6400 mg/m2 given i.v. over 3 h.

Phase I study of an immunomodulatory thalidomide analog, CC-4047, in relapsed or refractory multiple myeloma.

PURPOSE: To assess the safety, efficacy, and immunomodulatory effects of CC-4047 (Actimid; Celgene, San Diego, CA) in patients with relapsed or refractory myeloma. PATIENTS AND METHODS: Twenty-four relapsed or refractory patients were treated with a dose-escalating regimen of oral CC-4047. Clinical responses and adverse effects were identified, and peripheral T-cell subsets, serum cytokines, and proangiogenic factors were evaluated. RESULTS: CC-4047 was tolerated with no serious nonhematologic adverse events. All patients were eligible for analysis. Toxicity criteria during the initial 4 weeks of study were used to define the maximum-tolerated dose (MTD). During this period, one patient withdrew with a deep vein thrombosis (DVT) probably caused by an undiagnosed primary melanoma with lymphadenopathy in the groin, one patient withdrew because of progressive disease (PD), and three patients discontinued with neutropenia. Nineteen of 24 patients continued on treatment beyond 4 weeks to PD or development of a serious adverse event. Three further patients developed a DVT at 4, 9, and 11 months. Treatment resulted in a greater than 25% reduction in paraprotein in 67% of patients, 13 patients (54%) experienced a greater than 50% reduction in paraprotein, and four (17%) of 24 patients entered complete remission. The MTD was 2 mg/d. All patients showed increased CD45RO expression on CD4(+) and CD8(+) cells, with a concomitant decrease in CD45RA(+) cells. CC-4047 treatment was associated with significantly increased serum interleukin (IL)-2 receptor and IL-12 levels, which is consistent with activation of T cells and monocytes and macrophages. CONCLUSION: This study demonstrates the safety and efficacy of CC-4047. The MTD of CC-4047 orally was 2 mg/d. This is the first report demonstrating in vivo T-cell costimulation by this class of compound, supporting a potential role for CC-4047 as an immunostimulatory adjuvant treatment.

Pamidronate reduces skeletal morbidity in women with advanced breast cancer and lytic bone lesions: a randomized, placebo-controlled trial. Protocol 18 Aredia Breast Cancer Study Group.

PURPOSE: To assess whether pamidronate can reduce the frequency of skeletal morbidity in women with lytic bone metastases from breast cancer treated with hormone therapy. PATIENTS AND METHODS: Three hundred seventy-two women with breast cancer who had at least one lytic bone lesion and who were receiving hormonal therapy were randomized to receive 90 mg of pamidronate or placebo as a 2-hour intravenous infusion given in double-blind fashion every 4 weeks for 24 cycles. Patients were evaluated for skeletal complications: pathologic fractures, spinal cord compression, irradiation of or surgery on bone, or hypercalcemia. The skeletal morbidity rate (the ratio of the number of skeletal complications to the time on trial) was the primary efficacy variable. Bone pain, use of analgesics, quality of life, performance status, bone tumor response, and biochemical parameters were also evaluated. RESULTS: One hundred eighty-two patients who received pamidronate and 189 who received placebo were assessable. The skeletal morbidity rate was significantly reduced at 12, 18, and 24 cycles in patients treated with 90 mg of pamidronate (P = .028, .023, and .008, respectively). At 24 cycles, the proportion of patients having had any skeletal complication was 56% in the pamidronate group and 67% in the placebo group (P = .027). The time to the first skeletal complication was longer for patients receiving pamidronate than for those given placebo (P = .049). There was no statistical difference in survival or in objective bone response rate. Pamidronate was well tolerated. CONCLUSION: Treatment with 90 mg of pamidronate as a 2-hour intravenous infusion every 4 weeks in addition to hormonal therapy significantly reduces skeletal morbidity from osteolytic metastases.

Long-term prevention of skeletal complications of metastatic breast cancer with pamidronate. Protocol 19 Aredia Breast Cancer Study Group.

PURPOSE: Pamidronate, an aminobisphosphonate, has been shown to lower the risk of skeletal complications associated with lytic bone lesions for up to 1 year in women with stage IV breast cancer who received chemotherapy. We studied the long-term effectiveness and safety of continued treatment with intravenous pamidronate infusions for up to 2 years. PATIENTS AND METHODS: Three hundred eighty-two women with metastatic breast cancer and lytic bone lesions who received chemotherapy were randomly assigned to receive either 90 mg of pamidronate or placebo intravenously every 3 to 4 weeks in this double-blind, multicenter, parallel-group trial. Patients were evaluated monthly for 2 years for skeletal complications, which included pathologic fractures, need for radiation or surgery to treat bone complications, spinal cord compression, and hypercalcemia. Bone pain, analgesic use, bone biochemical markers, performance status, quality of life, radiologic response in bone, and survival were also evaluated. RESULTS: As in the first year of treatment, the proportion of patients with any skeletal complication was significantly less for the pamidronate than the placebo group at 15, 18, 21, and 24 months (P < .001). The proportions of patients with any pathologic fracture (i.e., vertebral and nonvertebral fractures), need for radiation or surgery to treat bone complications, and hypercalcemia were also statistically less for the pamidronate than the placebo group. The median time to the first skeletal complication was 13.9 months in the pamidronate-treated women and 7.0 months in the placebo group (P < .001). Long-term treatment did not result in any unexpected adverse events. Survival did not differ between the two groups. CONCLUSION: The risk for osteolytic bone lesion complications in metastatic breast cancer was significantly decreased with monthly infusions of 90 mg of pamidronate, and this effect was maintained for at least 2 years. Pamidronate is a useful adjunct to standard chemotherapy in the palliative treatment of metastatic breast cancer.

Long-term pamidronate treatment of advanced multiple myeloma patients reduces skeletal events. Myeloma Aredia Study Group.

PURPOSE: To determine the efficacy and safety of 21 monthly cycles of pamidronate therapy in patients with advanced multiple myeloma. PATIENTS AND METHODS: Patients with stage III myeloma and at least one lytic lesion received either placebo or pamidronate 90 mg intravenously administered as a 4-hour infusion monthly for 21 cycles. At study entry, the patients were stratified according to whether they were to receive first-line (stratum 1) or second-line (stratum 2) antimyeloma chemotherapy. Skeletal events (pathologic fracture, radiation or surgery to bone, and spinal cord compression) and hypercalcemia were assessed monthly. RESULTS: The results of the first nine previously reported cycles are extended to 21 cycles. Of the 392 randomized patients, efficacy could be evaluated in 198 who received pamidronate and 179 who received placebo. After 21 cycles, the proportion of patients who developed any skeletal event was lower in the pamidronate-group (P = .015). The mean number of skeletal events per year was less in the pamidronate-group (1.3) than in placebo-treated patients (2.2; P = .008). Although survival was not different between the pamidronate-treated group and placebo patients overall, stratum 2 patients who received pamidronate lived longer than those who received placebo (14 v 21 months, P = .041). Pamidronate was safe and well tolerated during the 21 cycles of therapy. CONCLUSION: Long-term monthly infusions of pamidronate as an adjunct to chemotherapy are superior to chemotherapy alone in reducing skeletal events in stage III multiple myeloma patients, and may improve the survival of patients on salvage therapy.

Rhyme or reason: RNA-arginine interactions and the genetic code.

Theories about the origin of the genetic code require specific recognition between nucleic acids and amino acids at some stage of the code's evolution. A statistical analysis of arginine-binding RNA aptamers now offers the opportunity to test such interactions and provides the strongest support for an intrinsic affinity between any amino acid and its codons.

Hereditary warfarin resistance. Investigation of a rare phenomenon.

A 57-year-old black woman required a daily dosage of 50 mg of warfarin sodium to maintain her prothrombin time in a therapeutic range. The central volume of distribution and clearance of warfarin were normal for this patient. These findings, combined with the patient's requirement for plasma warfarin levels four times greater than those usually required to achieve adequate anticoagulation, indicated that the relative resistance was due to altered pharmacodynamics of warfarin. The only child of the propositus, a daughter, showed a similar relative resistance, confirming that this family is the third to be reported with hereditary resistance to warfarin.

Treatment of cancer-associated hypercalcemia. Double-blind comparison of rapid and slow intravenous infusion regimens of pamidronate disodium and saline alone.

BACKGROUND: We assessed the effects of 60-mg single doses of pamidronate disodium compared with saline alone in the treatment of cancer-associated hypercalcemia. METHODS: After pretreatment hydration, patients with corrected serum calcium concentrations of 3.0 mmol/L (12 mg/dL) or greater secondary to cancer were randomized to double-blind treatment with a single infusion of pamidronate disodium, 60 mg, over either 4 or 24 hours or continued infusions of 0.9% saline alone (n = 23 per group). Corrected serum calcium levels were measured daily for 7 days of inpatient evaluation. RESULTS: Response rates for both of the pamidronate regimens were significantly (P < .05) higher than that for saline alone. A complete response to treatment (corrected serum calcium concentration normalized) was observed for five (22%), 18 (78%), and 14 (61%) patients, respectively, who received saline alone, 4-hour infusion of pamidronate, and 24-hour infusion of pamidronate. There were no significant differences between the two pamidronate regimens. Median durations of complete response were 6, 6, and 11 days, respectively, and median times to relapse (includes complete plus partial responders and nonresponders) were 0, 7, and 7 days, respectively. Pamidronate was well tolerated as assessed by all clinical and laboratory measures, regardless of the time of infusion. CONCLUSIONS: A 4-hour infusion of pamidronate disodium, 60 mg, was as safe and effective as a 24-hour infusion, and both were superior to saline alone in lowering corrected serum calcium concentrations in patients with cancer-associated hypercalcemia.

Effects of anti-CD33 blocked ricin immunotoxin on the capacity of CD34+ human marrow cells to establish in vitro hematopoiesis in long-term marrow cultures.

Human marrow cells that express the CD34 antigen but lack CD33 are able to initiate sustained, multilineage in vitro hematopoiesis in long-term Dexter cultures and are believed to include the primitive stem cells responsible for effecting long-term hematopoietic reconstitution in vivo following marrow transplantation. In studies described in this report we investigated the effects of a novel anti-CD33 immunotoxin on the clonogenic potential of normal human CD34+ marrow cells and on the ability of these cells to initiate hematopoiesis in two-stage Dexter cultures (long-term marrow cultures, LTMC). This immunotoxin (anti-CD33-bR), shown previously to kill both clonogenic myelogenous leukemia cells and normal mature myeloid progenitor cells (granulocyte-macrophage colony-forming units, CFU-GM), consists of an anti-CD33 monoclonal antibody conjugated to purified ricin that has been modified by blocking the carbohydrate binding domains of the ricin B-chain to eliminate nonspecific binding. For our studies, normal CD34+ human marrow cells were isolated from the light-density (less than 1.070 g/ml) cells of aspirated marrow by positive selection with immunomagnetic beads linked to the monoclonal antibody K6.1. These cell isolates were highly enriched with both multipotential and lineage-restricted clonogenic, hematopoietic progenitors (mixed lineage colony-forming units, CFU-Mix; CFU-GM; and erythroid burst-forming units, BFU-E) which constituted greater than or equal to 20% of the cells. Recovery of clonogenic progenitors from these CD34+ cell preparations, following treatment with anti-CD33-bR (10 nM), was reduced by greater than or equal to 85% for CFU-GM and 20%-40% for CFU-Mix and BFU-E. However, the capacity of these cells to initiate hematopoietic LTMC was preserved. Indeed, the production of high proliferative potential (HPP) CFU-GM, BFU-E, and CFU-Mix in cultures seeded with 10(5) anti-CD33-bR-treated CD34+ marrow cells was substantially greater than that observed in LTMC seeded with equivalent numbers of untreated CD34+ cells. Moreover, concentrations of long-term culture initiating cells in CD34+ cell isolates, quantified by a limiting dilution technique, were found to be increased following anti-CD33-bR treatment. These findings support the potential usefulness of anti-CD33-bR for in vitro marrow purging or in vivo treatment to eliminate CD33+ leukemic clones, while sparing normal CD34+/CD33- stem cells that support normal hematopoiesis and hematopoietic reconstitution in vivo.

Efficiency of human HLA-mismatched CD34+ cells from unrelated donors in establishing in vitro hematopoiesis in allogeneic long-term marrow cultures.

We have examined the capacity of highly purified human CD34+ marrow cell isolates from unrelated, HLA-mismatched donors to establish in vitro hematopoiesis on recipient marrow stromal cells in 2-stage hematopoietic long-term marrow cultures (H-LTMC). HLA-typing of both peripheral blood mononuclear cells and CD34+ marrow cells was performed for both HLA class I and HLA class II antigens for eight healthy individuals. Significant antigenic mismatches for these molecules ranged from three to six antigens for each recipient-donor pair. Comparison of MHC antigen expression by peripheral blood cells and CD34+ marrow cell isolates confirmed the presence of identical HLA-A, -B, and -C, and -DR specificities on the surface of these cells. Typing of -DQ specificities, however, was not consistently reactive on CD34+ cells. The > or = 20% plating efficiency of purified CD34+ cells for BFU-E, CFU-GM, and CFU-MIX allowed us to use inoculum doses of 10(3), 10(4), and 10(5) cells to determine the efficiency of allogeneic CD34+ cells in achieving in vitro engraftment and the establishment of hematopoiesis in H-LTMC. Engraftment of adherent BFU-E, CFU-GM, and CFU-MIX was equally efficient for autologous and allogeneic CD34+ cells. In vitro hematopoiesis reflected by the cumulative recoveries of progenitor cells over time was also equivalent for allogeneic and autologous CD34+ cells. These results demonstrate that highly purified, HLA-mismatched CD34+ marrow cells proliferate and establish in vitro hematopoiesis as efficiently as autologous cells in marrow derived stromal cell cultures and confirm that interactions between stromal cells and highly purified CD34+, DR-, and CD34+, DR+ marrow cell isolates are not MHC-restricted.

Evidence for a factor in normal human serum that induces human neutrophilic granulocyte end-stage maturation in vitro.

The end-stage maturation of neutrophilic granulocyte precursor cells isolated from normal human bone marrow by Ficoll density centrifugation was studied in a liquid culture assay system used previously to study the maturation of guinea pig granulocyte precursors. Dialyzed normal human serum induced end-stage morphological maturation of human granulocyte precursors and this induction was proportional to a serum level of up to 5.0% in the assay medium. At serum concentrations greater than 5.0% a pronounced inhibition of maturation was observed. Passage of serum through a DEAE-Fractogel 650S column equilibrated with 0.01 M phosphate buffer (pH 7.0) resulted in the binding of the end-stage granulocyte maturation factor to the column. The activity eluted from the column in a fraction containing 17% of the starting serum protein that was inhibitor-free and was also capable of inducing the appearance of granulocyte alkaline phosphatase, a specific biochemical marker for granulocyte end-stage maturation. GMF is most likely a protein since it was destroyed by protease digestion. The data also indicate that neither purified human transferrin nor human recombinant granulocyte colony-stimulating factor can substitute for human serum GMF as a granulocyte end-stage maturation factor in this assay system. It was observed, however, that purified human transferrin greatly potentiated the effect of GMF suggesting that transferrin plays a supporting role in the end-stage maturation of human granulocytes in vitro. To our knowledge the evidence presented here indicates for the first time the existence of a neutrophilic granulocyte end-stage maturation factor in normal human serum.

The effect of labor on the rheologic response of chorioamniotic membranes.

A study of chorioamniotic membranes was undertaken in 2 term populations. One group of women delivered vaginally after normal labor (N = 41), the other by elective cesarean section (N = 41). Rheologic properties were measured in an experimental environment. The membranes in each group responded similarly while intact. Those membranes subject to labor, however, ruptured earlier in cyclic testing. They also required more time to dissipate applied stress. This stress response pattern is similar to that seen with rupture of amorphous materials in which multiple flaws or cracks are aggravated by stress testing. The clinical problem of premature rupture of the membranes may occur by a phenomenon that produces flaws in their structure. The data suggest that these flaws may be aggravated by labor-like uterine activity.

Pharmacokinetics of pamidronate disodium in patients with cancer with normal or impaired renal function.

Pamidronate is a second-generation bisphosphonate that undergoes negligible biodegradation and is eliminated exclusively by renal excretions. Nineteen cancer patients were stratified according to baseline creatinine clearance (Clcr): group I, Clcr > 90 mL/min (n = 6); group II, Clcr 61 mL/min to 90 mL/min (n = 6); group III, Clcr 30 mL/min to 60 mL/min (n = 3); group IV, Clcr < 30 mL/min (n = 4). All patients received a single, 90-mg dose of pamidronate disodium administered in a 4-hour intravenous infusion. Plasma and urine samples were collected at intervals up to 36 and 120 hours, respectively, after the start of infusion and were assayed for pamidronate, using validated high-performance liquid chromatography. Pamidronate's pharmacokinetics were characterized by a short distribution phase (2-3 hours) followed by rapid elimination of the drug in urine. Elimination of pamidronate was slower in patients in group IV with a mean +/- standard deviation area under the plasma concentration-time curve (AUC0-36) of 19.0 +/- 4.60 micrograms.hr/mL compared with 8.1 +/- 3.13 micrograms.hr/mL in patients in group I. A linear relationship in Clcr was observed for AUC0-36 (r = 0.67), urinary excretion (r = 0.69), and renal clearance (r = 0.81). Renal clearance was proportional to Clcr for patients in all four renal-function groups. In the treatment of bone metastases of malignancy, successive doses of pamidronate are generally separated by weeks; thus, plasma accumulation in patients with renal impairment is not expected to be clinically relevant. A reduction in dose of pamidronate disodium should not be necessary in cancer patients with renal impairment.

Effects of varying electrode site placements on the torque output of an electrically stimulated involuntary quadriceps femoris muscle contraction.

The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense. At the time this study was performed, LTs Ferguson, Blackley, Knight, and Sutlive were students in the US. Army-Baylor University Graduate Program in Physical Therapy. This research was performed in partial fulfillment of their requirements for the Master of Physical Therapy Degrees.The purpose of this study was to evaluate the effects of varying electrode placement on the torque output of an electrically stimulated involuntary quadriceps femoris muscle contraction. Twenty-two volunteer subjects (18 men, 4 women) with a mean age of 21.7 years received electrical stimulation according to a randomized treatment order which included: Femoral nerve and 1) vastus medialis (VM), 2) rectus femoris (RF), 3) vastus lateralis (VL), 4) opposite quadriceps (OQ), and 5) the ipsilateral vastus medialis and vastus lateralis (VM/VL). The subject's knee was placed in 60 degrees of flexion, and the isokinetic dynamometer set at 0 degrees /sec. The peak torque produced by the involuntary quadriceps contraction was measured as a percentage of maximum voluntary isometric contraction (MVIC). An analysis of variance with repeated measures was used to examine the data. The results indicated the mean percentages of MVIC produced by stimulating the VM, VL, and RF sites were significantly greater (p