Sympathetic blockade of isolated rat hindlimbs by intra-arterial guanethidine: the effect on blood flow and arterial-venous shunting

In order to improve the understanding of the role of sympathetic nerve degeneration in reimplantation failure, the hindlimbs of eight rats (Group I) underwent near-complete amputation. The soft tissues of the hindlimb were transected at the proximal thigh with the femoral artery, vein and femur left intact. The femoral vessels were clamped and guanethidine was infused into a branch of the femoral artery of the right leg of each animal, while saline was injected into the left leg. The clamps were removed after 15 minutes. A baseline preoperative injection of radiolabeled microspheres was made, and subsequent injections at 6, 12, 18, and 24 hours postoperation. Twelve rats (Group II) were then used to assess the amount of arterial-venous shunting preoperatively (n = 6) and at 18 hours postoperation (n = 6), by venous sampling. Blood flow to both limbs increased postoperation, but there was significantly more flow in the guanethidine treated limb at 18 and 24 hours postoperation. The amount of shunting was approximately 50% in both limbs at 18 hours, as compared to 10% preoperation. These results highlight the potential benefit of guanethidine and other sympathetic blocking agents in reimplantation to increase blood flow, decrease tissue ischemia and increase anastomotic patency rates. They also suggest that sympathetic nerve degeneration did not affect the volume of arterial-venous shunting in this model, but the difference in blood flow was likely due to arteriolar vasospasm. Further study is needed to elucidate the clinical significance of sympathetic nerve degeneration in reimplantation failure.     

Bone marrow and renal injury associated with haloalkene cysteine conjugates in calves

Almost 40 years ago, it was reported that cattle-feed which had been extracted with hot trichloroethylene and then fed to calves produced renal injury and a fatal aplastic anaemia. The toxic factor was subsequently identified as S-(1,2-dichlorovinyl)-L-cysteine (DCVC). These original findings have been confirmed, a single intravenous dose of DCVC at 4 mg/kg, or 0.4 mg/kg intravenously per day administered for 10 days to calves produced aplastic anaemia, and renal injury after a single dose of 4 mg/kg. The toxicity to calves of a number of other haloalkene cysteine conjugates has been examined to ascertain whether, like DCVC, they produce bone marrow and renal injury. Intravenous administration of the N-acetyl cysteine conjugate of DCVC produced renal but not bone marrow injury at a molar equivalent dose to DCVC, indicating that the calf can deacetylate the mercapturic acid and further that sufficient chemical had reached the kidney to be a substrate for the enzyme cysteine conjugate beta-lyase. However, intravenous administration of the alpha-methyl analogue of DCVC, which cannot undergo metabolism via the enzyme cysteine conjugate beta-lyase, was without toxicity at doses about five-fold higher than DCVC. These latter findings provide strong evidence that metabolism of DCVC via the enzyme beta-lyase is necessary for bone marrow and renal injury to occur. The cysteine conjugates of perchloroethylene and hexachloro-1,3-butadiene(HCBD) when given intravenously to calves at molar equivalent doses to DCVC, or above, did not produce either bone marrow or renal injury. In contrast, intravenous administration of the cysteine conjugate of tetrafluoroethylene (TFEC) produced severe renal tubular injury in calves without affecting the bone marrow. In vitro studies with these haloalkene cysteine conjugates showed, like DCVC, that they were good substrates for calf renal cysteine conjugate beta-lyase and toxic to renal cells as judged by their ability to reduce organic anion and cation transport by slices of calf renal cortex and inhibit the renal enzyme glutathione reductase. Calves were also dosed either orally or intravenously with HCBD to assess its toxicity. HCBD at higher molar equivalent doses than DCVC produced mid-zonal necrosis in the liver, renal tubular necrosis but no bone marrow injury in calves. The key findings emerging from these studies are (1) that none of the other cysteine conjugates, at molar equivalent doses to DCVC and above, produce bone marrow injury in calves, (2) TFEC produced only renal injury, suggesting that sufficient of the other conjugates had not reached the kidney for metabolism by beta-lyase to produce cytotoxicity and (3) that HCBD itself is more toxic than its cysteine or mercapturic acid conjugate, suggesting that pharmaco-kinetics and disposition are important factors in determining the toxicity of these conjugates to calves. Further studies are needed to understand the basis for the selective toxicity of DCVC to the bone marrow of calves.     

Polylysine decelerates kinetics of negatively charged gramicidin channels as shown by sensitized photoinactivation

Effect of a cationic polymer, poly(L-lysine), on the kinetic properties of ionic channels formed by neutral gramicidin A (gA) and its negatively charged analogue O-pyromellitylgramicidin (OPg) in a bilayer lipid membrane is studied using a method of sensitized photoinactivation. This newly developed method is based on the analysis of transmembrane current transients induced by a flash in the presence of a photosensitizer. It has been shown previously that the time course of the flash-induced current decrease in most cases follows a single exponential decay with an exponential factor (tau, the characteristic time of photoinactivation) that correlates well with the single-channel lifetime. Addition of polylysine does not affect tau for gA channels, but causes a substantial increase in tau for OPg channels. This effect is reversed by addition of polyacrylic acid. The deceleration of the photoinactivation kinetics is ascribed to electrostatic interaction of polylysine with OPg probably resulting in OPg clustering. The latter can stabilize the channel state by reducing the rotational and lateral mobility of OPg monomers and dimers, and thus increase the single channel lifetime.     

Tandem SH2 domains confer high specificity in tyrosine kinase signaling

SH2 domain proteins transmit intracellular signals initiated by activated tyrosine kinase-linked receptors. Recent three-dimensional structures suggest mechanisms by which tandem SH2 domains might confer higher specificity than individual SH2 domains. To test this, binding studies were conducted with tandem domains from the five signaling enzymes: phosphatidylinositol 3-kinase p85, ZAP-70, Syk, SHP-2, and phospholipase C-gamma1. Bisphosphorylated TAMs (tyrosine-based activation motifs) were derived from biologically relevant sites in platelet-derived growth factor, T cell, B cell, and high affinity IgE receptors and the receptor substrates IRS-1 (insulin receptor substrate-1) and SHPS-1/SIRP. Each tandem SH2 domain binds a distinct TAM corresponding to its appropriate biological partner with highest affinity (0.5-3.0 nM). Alternative TAMs bind the tandem SH2 domains with 1,000- to >10,000-fold lower affinity than biologically relevant TAMs. This level of specificity is significantly greater than the approximately 20-50-fold typically seen for individual SH2 domains. We conclude that high biological specificity is conferred by the simultaneous interaction of two SH2 domains in a signaling enzyme with bisphosphorylated TAMs in activated receptors and substrates.     

Contribution of growth hormone and IGF-I to early diabetic nephropathy in type 1 diabetes

In children and adolescents with type 1 diabetes, we have reported an association between duration of puberty and the prevalence of nephromegaly and microalbuminuria (MA), which are early markers of diabetic nephropathy. Growth hormone (GH), IGF-I, testosterone, and prorenin are potential mediators of this effect. This study examined the relationship of these hormonal factors to kidney volume (KV) and MA in 155 subjects (78 males, age 13.2 +/- 3.5 years [mean +/- SD]) with similar diabetes duration (6.83 +/- 1.6 years) but varying pubertal experience (0-10 years). KV (by ultrasound), plasma IGF-I, testosterone, prorenin, and NaLi countertransport, and urinary albumin, urinary GH, and urinary IGF-I from three 24-h collections were measured. Multiple regression analysis showed that BSA (P < 0.0001) and urinary IGF-I (P = 0.001) were significantly associated with KV. MA subjects (albumin excretion rate 15-200 microg/min) had higher urinary IGF-I (P = 0.005) and urinary GH (P = 0.05) compared with normoalbuminuric subjects. Only 9% of the variance in urinary IGF-I could be attributed to plasma IGF-I (r = 0.30, P < 0.0001). Testosterone and prorenin were not associated with MA, but they were associated with KV in univariate analyses. The strong association of urinary IGF-I with KV, a marker for glomerular hypertrophy, and of both urinary IGF-I and urinary GH with MA suggests a role for these growth factors in the development of human diabetic nephropathy. Together, these data support animal studies that have shown that renal GH and IGF-I may contribute significantly to the pathogenesis of early diabetic nephropathy.     

Stage T1-2 prostate cancer: a multivariate analysis of factors affecting biochemical and clinical failures after radical prostatectomy

PURPOSE: Prostate-specific antigen (PSA) is extensively used in case selection and outcome evaluation after treatment of clinically localized prostate cancer. Careful case selection can have a profound impact on pathologic findings and ultimate outcome. In addition, salvage treatment is frequently initiated at the time of biochemical relapse rather than clinical recurrence. Consequently, patterns of failure can be significantly altered compared to previous times when PSA was not available. To better understand the impact of PSA on pathologic findings, outcome, and salvage treatment, we reviewed our experience in the PSA era with clinical Stage T1-2 prostate cancer treated with radical prostatectomy. METHODS AND MATERIALS: Between 1987 and 1993, 423 cases could be identified with clinical Stage T1-2 prostate cancer treated with radical prostatectomy. The distribution of cases by pretreatment PSA levels was as follows: < or = 4 ng/ml (18%), 4-10 ng/ml (42%), 10-20 ng/ml (21%), > 20 ng/ml (14%), and unknown (5%). The median pretreatment PSA level for the entire group was 8.0 ng/ml. Sixteen patients received adjuvant or neoadjuvant androgen suppression and 13 received postoperative radiotherapy. Only 31 patients (7%) had pathologically positive pelvic lymph nodes. The overall margin involvement rate was 46%. Fifty-three percent of patients had surgical Gleason scores > or = 7, and 65% had extracapsular extension. The median follow-up time was 41 months. RESULTS: The projected overall survival at 7 years after surgery was 90%. The 5-year clinical relapse-free survival rate was 84%. At 5 years, the local control and distant failure rates were 92% and 91%, respectively. Biochemical relapse was defined as a detectable or rising PSA level after prostatectomy. The 5-year biochemical relapse-free survival (bRFS) rate was 59%. The 5-year RFS was 88% in patients with preoperative PSA levels < or = 4, 62% for 4-10, 48% for 10-20, and 31% for > 20. Combining the two independent preoperative variables, iPSA and biopsy GS (bGS), two risks groups were defined: low risk [initial PSA (iPSA) levels < or = 10.0 and bGS < or = 6] and high risk (iPSA levels > 10.0 ng/ml or bGS > or = 7). The 5-year bRFS rate for the low-risk cases was 81% vs. 40% for high-risk cases (p < 0.001). On multivariate analysis, three factors independently predicted biochemical relapse: iPSA levels (p = 0.005), Gleason score from the surgical specimen (sGS) (p = 0.002), and positive surgical margins (p < or = 0.001). The 5-year bRFS rates for margin positive vs. margin negative patients were 37% vs. 78%, respectively. The 5-year bRFS rates for GS > or = 7 vs. GS > or = 6 were 42% vs. 80%, respectively. All clinical relapses were accompanied by a rise in PSA. In patients who manifested biochemical failure followed by a clinical failure, the median interval between the PSA rise and clinical failure was 19 months (range 7-71). Margin involvement was the only independent predictor of local failure (p = 0.019). The 5-year local failure-free survival for negative margin cases was 96% vs. 87% for positive margin cases (p = 0.012). Lymph node (LN) involvement and high-risk group were the two independent predictors of distant failure. The 5-year distant failure-free survival for negative LN cases was 94% vs. 67% for positive LN cases (p < 0.001). The 5-year distant failure-free survival for low-risk cases was 97% vs. 85% for high-risk cases (p = 0.005). For the 124 patients failing biochemically, 85 were observed and 39 were treated either with radiation or androgen deprivation. With a median follow-up of 32 months, the clinical disease relapse-free survival was 79% for the treated patients vs. only 32% for the patients observed (p < 0.001). CONCLUSION: Pretreatment PSA is the most potent clinical factor independently predicting biochemical relapse, thereby allowing markedly better case selection. Achieving negative margins, even in relatively advanced disease, provides excellent lon     

Rapid inhalation induction in children: 8% sevoflurane compared with 5% halothane

BACKGROUND: Ultrasonography (US) by acknowledged experts enhances the diagnostic performance and reduces the rate of negative laparotomies in patients with suspected acute appendicitis (AA). METHODS: The diagnostic accuracy and clinical impact of routine US performed by surgical residents was prospectively studied in 504 unselected patients admitted for AA. Clinical and US findings were correlated with laparotomy findings and pathological outcome in 135 patients (113 cases with proven AA, prevalence 22.4%) and clinical as well as follow-up data were compared in the remainder. RESULTS: The overall accuracy, sensitivity, and specificity of the clinical diagnosis of AA were 84.9%, 51.3%, and 94.6% and those of US were 93. 6%, 83.1%, and 96.6%. Joint evaluation of the results from clinical evaluation and US further improved diagnostic performance (accuracy 93.4%, sensitivity 84.1%, specificity 96.2) and significantly reduced the rate of diagnostic errors to 3.4% (p < 0.001) and unnecessary laparotomies to 9.6% (p < 0.01) in patients with suspected AA. CONCLUSIONS: Ultrasonographic evaluation of the patient with suspected AA is considered to be of value in surgical practice.