Mutant protein in Huntington disease is resistant to proteolysis in affected brain.

The cause of Huntington disease pathophysiology is unknown, but a major hypothesis suggests that toxicity arises from the cleavage and accumulation of amino-terminal fragments containing an expanded polyglutamine region. In evaluating huntingtin protein (HD) from human brain, transgenic animals and cells, we observed, unexpectedly, that mutant HD is more resistant to proteolysis than normal HD. The N-terminal cleavage fragments we observed arise from the processing of normal HD and are sequestered by full-length mutant HD. Our results support a model in which inhibition of proteolysis of mutant HD leads to aggregation and toxicity through the sequestering of important targets, including normal HD.

Ultrafast infrared spectroscopy.

Recent advances in ultrafast infrared spectroscopy are described, including experimental details and fundamental limitations. The utility of this technique is illustrated with two recent examples.

Resonance Raman studies of Rieske-type proteins.

Resonance Raman (RR) spectra are reported for the [2Fe-2S] Rieske protein from Thermus thermophilus (TRP) and phthalate dioxygenase from Pseudomonas cepacia (PDO) as a function of pH and excitation wavelength. Depolarization ratio measurements are presented for the RR spectra of spinach ferredoxin (SFD), TRP, and PDO at 74 K. By comparison with previously published RR spectra of SFD, we suggest reasonable assignments for the spectra of TRP and PDO. The spectra of PDO exhibit virtually no pH dependence, while significant changes are observed in TRP spectra upon raising the pH from 7.3 to 10.1. One band near 270 cm-1, which consists of components at 266 cm-1 and 274 cm-1, is attributed to Fe(III)-N(His) stretching motions. We suggest that these two components arise from conformers having a protonated-hydrogen-bonded imidazole (266 cm-1) and deprotonated-hydrogen-bonded imidazolate (274 cm-1) coordinated to the Fe/S cluster and that the relative populations of the two species are pH-dependent; a simple structural model is proposed to account for this behavior in the respiratory-type Rieske proteins. In addition, we have identified RR peaks associated with the bridging and terminal sulfur atoms of the Fe-S-N cluster. The RR excitation profiles of peaks associated with these atoms are indistinguishable from each other in TRP (pH 7.3) and PDO and differ greatly from those of [2Fe-2S] ferrodoxins. The profiles are bimodal with maxima near 490 nm and > approx. 550 nm. By contrast, bands associated with the Fe-N stretch show a somewhat different enhancement profile. Upon reduction, RR peaks assigned to Fe-N vibrations are no longer observed, with the resulting spectrum being remarkably similar to that reported for reduced adrenodoxin. This indicates that only modes associated with Fe-S bonds are observed and supports the idea that the reducing electron resides on the iron atom coordinated to the two histidine residues. Taken as a whole, the data are consistent with an St2FeSb2Fe[N(His)]t2 structure for the Rieske-type cluster.

South African Indians show a high prevalence of NIDDM and bimodality in plasma glucose distribution patterns.

OBJECTIVE: To determine the prevalence of diabetes mellitus and impaired glucose tolerance (IGT) and to test for bimodality in the plasma glucose distribution in South African Indians. RESEARCH DESIGN AND METHODS: Subjects were selected by systematic cluster sampling in various areas of Durban. They underwent a modified glucose tolerance test whereby fasting and 2-h postglucose (75 g) plasma glucose levels were measured. The program MIX was used to test for bimodality in the plasma glucose distribution. RESULTS: We tested 2,479 subjects (1,441 women and 1,038 men). Based on the revised World Health Organization criteria, the crude prevalence of diabetes mellitus was 9.8%, and the crude prevalence of IGT was 5.8%; the age- and sex-adjusted prevalence was 13.0 and 6.9%, respectively. IGT was significantly more common in men (7.6%) than in women (4.4%). Obesity was a feature of both diabetes mellitus and IGT, particularly in women. Both fasting and 2-h plasma glucose values did not conform to a single normal distribution pattern in any age-group, whereas unequivocal evidence of bimodality was seen in the 55- to 74-year age-group of both sexes for fasting and 2-h glucose and also in the 2-h levels of men in the 25- to 34-year age-group. CONCLUSIONS: This study has highlighted a high prevalence of non-insulin-dependent diabetes mellitus in South African Indians and bimodality in the plasma glucose distribution.

Effect of colesevelam on faecal bile acids and bowel functions in diarrhoea-predominant irritable bowel syndrome.

BACKGROUND: About one-third of patients with IBS-diarrhoea (irritable bowel syndrome-D) have evidence of increased bile acid synthesis or excretion. AIMS: To assess effects of the bile acid sequestrant, colesevelam, on faecal excretion of BAs, hepatic BA synthesis and diarrhoea in IBS-D; to appraise whether individual or random stool samples accurately reflect 48-h total faecal bile acid excretion and proportions of the main bile acids excreted and to study the faecal fat excretion in response to colesevelam. METHODS: A single-centre, unblinded, single-dose trial of effects of colesevelam, 1875 mg [3 tablets (625 mg tablets)] orally, twice daily, for 10 days on total 48-h faecal bile acid excretion and fasting serum C4 (7α-hydroxy-4-cholesten-3-one; surrogate of hepatic bile acid synthesis). Stool diaries documented bowel functions for 8 days prior and 8 days during colesevelam treatment. Stool 48-h samples and fasting serum were collected for faecal fat, faecal bile acid and serum C4. RESULTS: Colesevelam was associated with significantly increased faecal total bile acid excretion and deoxycholic acid excretion, increased serum C4 and more solid stool consistency. There was a significant inverse correlation between number of bowel movements per week and the total bile acid sequestered into stool during the last 48 h of treatment. Random stool samples did not accurately reflect 48-h total or individual faecal bile acid excretion. Sequestration of bile acids by colesevelam did not increase faecal fat. CONCLUSIONS: Colesevelam increases delivery of bile acids to stool while improving stool consistency, and increases hepatic bile acid synthesis, avoiding steatorrhoea in patients with IBS-D. Overall effects are consistent with luminal bile acid sequestration by colesevelam.

Structural heterogeneity of the various forms of apomyoglobin: implications for protein folding.

Temperature-induced denaturation transitions of different structural forms of apomyoglobin were studied monitoring intrinsic tryptophan fluorescence. It was found that the tryptophans are effectively screened from solvent both in native and acid forms throughout most of the temperature range tested. Thus, the tryptophans' surrounding do not show a considerable change in structure where major protein conformational transitions have been found in apomyoglobin using other techniques. At high temperatures and under strong destabilizing conditions, the tryptophans' fluorescence parameters show sigmoidal thermal denaturation. These results, combined with previous studies, show that the structure of this protein is heterogeneous, including native-like (tightly packed) and molten globule-like substructures that exhibit conformation (denaturation) transitions under different conditions of pH and temperature (and denaturants). The results suggest that the folding of this protein proceeds via two "nucleation" events whereby native-like contacts are formed. One of these events, which involves AGH "core" formation, appears to occur very early in the folding process, even before significant hydrophobic collapse in the rest of the protein molecule. From the current studies and other results, a rather detailed picture of the folding of myoglobin is presented, on the level of specific structures and their thermodynamical properties as well as formation kinetics.

Bound water in the proton translocation mechanism of the haem-copper oxidases.

We address the molecular mechanism by which the haem-copper oxidases translocate protons. Reduction of O2 to water takes place at a haem iron-copper (CuB) centre, and protons enter from one side of the membrane through a 'channel' structure in the enzyme. Statistical-mechanical calculations predict bound water molecules within this channel, and mutagenesis experiments show that breaking this water structure impedes proton translocation. Hydrogen-bonded water molecules connect the channel further via a conserved glutamic acid residue to a histidine ligand of CuB. The glutamic acid side chain may have to move during proton transfer because proton translocation is abolished if it is forced to interact with a nearby lysine or arginine. Perturbing the CuB ligand structure shifts an infrared mode that may be ascribed to the O-H stretch of bound water. This is sensitive to mutations of the glutamic acid, supporting its connectivity to the histidine. These results suggest key roles of bound water, the glutamic acid and the histidine copper ligand in the mechanism of proton translocation.

Comparison of penile duplex ultrasonography to pudendal arteriography. Variant penile arterial anatomy affects interpretation of duplex ultrasonography.

RATIONALE AND OBJECTIVES: Duplex ultrasonography is currently used as a noninvasive imaging modality for the functional evaluation of penile blood flow in impotent men. However, the accuracy of this test is controversial. The objective of this study was to determine the sensitivity and specificity of duplex ultrasonography, to assess the ultrasonographic parameters most predictive of arterial disease, and to evaluate the causes of misinterpretation of duplex ultrasound studies. METHODS: Duplex ultrasonography and pudendal arteriography were performed on 42 impotent men during a 4-year prospective study. The predictive power of the following ultrasonographic parameters were analyzed: cavernosal arterial diameter, peak blood flow velocity, and pulsations on real-time ultrasonography. RESULTS: The results of both studies were concordant in 81% of the patients with a 77% sensitivity and 85% specificity for ultrasonography when using arteriography as the gold standard. Arterial pulsations and peak blood flow velocity were most predictive, whereas dilation was not helpful. Variant penile arterial anatomy was present in 83% of the patients and was the most frequent cause of misinterpretation of duplex ultrasonography. CONCLUSION: Duplex ultrasonography is a fairly reliable screening test for arterial disease in impotent men. Visualization of arterial pulsations and measurement of peak blood flow velocity are the best predictors of arterial function. Awareness of the potential arterial anomalies may help reduce misinterpretation of ultrasonography. Arteriography is necessary in any patient being considered for penile arterial surgery because of the high frequency of anatomic variations.

CT features of renal cell carcinoma with emphasis on relation to tumor size.

Computed tomography (CT) is the current standard for diagnosing and staging renal cell carcinoma (RCC). Although general diagnostic guidelines exist, no large studies to date have delineated the CT features of RCC. We reviewed the CT appearances of 78 pathologically proven RCCs. Of the 61 RCCs larger than 50 mm (78%) there was imaging evidence of extrarenal spread (87%), intratumoral necrosis (61%) and differential growth rates within the tumor (64%). Tumors 50 mm or smaller often had a "benign" appearance with sharp, rounded margins (88%), homogeneous density (65%), and distinct interface with the kidney (82%). The significance of these lesions should not be underestimated. Although RCCs often showed transient marked enhancement after bolus contrast material injection (41%), during the infusion phase 97% were hypodense compared with the kidney regardless of tumor size. Calcifications were visible in 31% of RCCs. Although 22% of RCCs were predominantly cystic, none fulfilled all CT criteria of simple renal cysts.

Testicular germ cell tumors in HLA-genotype non-twin brothers.

The diagnosis of metastatic testicular carcinoma in a thirty-three-year-old man and his nineteen-year-old brother is reported. Histologically, the tumor of the older brother consisted predominantly of embryonal carcinoma with minor components of seminoma and adult teratoma; the tumor of the younger brother consisted entirely of embryonal carcinoma. Since previous reports suggest the possibility that the HLA genotype may be a factor in the etiology of testicular cancer, we typed the parents and four children of this family. The two affected brothers shared a paternal HLA-A3, Cw-,B7,DR2 haplotype that had not been transmitted to the two other living siblings. Analysis of the distribution of HLA haplotypes of the affected non-twin brothers of this family and those of three other non-twin pairs of brothers that have been reported showed that the affected pairs in each family shared one HLA haplotype. The differences between the expected and the observed distribution of HLA haplotypes in the four sibling pairs is not statistically significant, perhaps because of the small number of patients typed. Two of the four pairs shared a common haplotype. Additional family studies are required to establish a genetic origin of testicular tumors and to determine whether or not a "testicular carcinoma disease" gene is linked to the HLA complex. A large number of multicase families will be required for linkage analysis.

Treatment of HeLa cells with bacterial water extracts inhibits Shigella flexneri invasion.

Pathogenesis mediated by Shigella flexneri requires invasion of the gastrointestinal epithelium. It has been previously shown that HeLa cells challenged with S. flexneri show alterations in their phosphotyrosine-containing protein profile. In this report, we demonstrated that bacterial water extracts (WE) abrogated the invasion of HeLa cells by S. flexneri in a dose-dependent manner. A proteinaceous component of S. flexneri was shown to be responsible for this inhibitory activity. Proteins encoded on the 140-MDa plasmid were not responsible for the observed inhibition. WE from other Gram-negative bacteria also inhibited Shigella invasion of HeLa cells pretreated with WE showed changes in the profile and the intensity of phosphotyrosine-containing protein bands. These data were consistent with a surface protein component in WE which initiated aberrant host cell signaling at the membrane which may account for the inhibition of bacterial entry.

Shigella flexneri-HeLa cell interactions: a putative role for host cell protein kinases.

Epithelial cell invasion has been shown to be a prerequisite for Shigella flexneri virulence. Recently, we have documented the induction of transcription factor DNA binding activities as a result of S. flexneri challenge of HeLa cells. In this report, we show that HeLa cells challenged with S. flexneri display differences in phosphotyrosine-containing proteins. These changes are detected as early as 5 min post-challenge. Challenge with a noninvasive ipaB mutant strain resulted in the induction of a similar, but less intense, profile of phosphotyrosine-containing host cell proteins. Phosphotyrosine-containing proteins could be detected in S. flexneri, but were unique from those detected following HeLa cell challenge. S. flexneri invasion of HeLa cell monolayers was reduced by treatment with protein kinase inhibitors. These data suggest a role for protein kinases in the initial response of host cells to S. flexneri.

Update on interventional uroradiology.

From its humble beginnings as a method of expediently decompressing the obstructed kidney, the field of interventional uroradiology has evolved in the hands of urologists and interventional radiologists to a means of addressing myriad problems in the urinary tract and has changed the day-to-day practice of urology. The foundation of interventional uroradiology is the creation of an appropriate entry into the urinary system. After a review of this basic procedure, extensions of the technique and new applications of emerging technology are reviewed.

Do's and don't's of percutaneous nephrostomy.

Percutaneous nephrostomy procedures generally are safe. The associated mortality rate is approximately 0.04%, and the incidence of important complications is 5% (2-4). To minimize complications, certain precautions always should be followed. First, radiologists should perform a preprocedural evaluation of the patient, with correction of marked coagulopathy or thrombocytopenia before all but the most emergent procedures. Second, antibiotics should be administered routinely before nephrostomy drainage; the choice of antibiotics can be based on the specific patient's risk factors for bacteriuria. To minimize the risk of clinically important renal vascular damage, radiologists should do the following: 1. Always achieve adequate visualization of the calices. 2. Identify a posterior calix for puncture that will give access to the appropriate segment of the kidney for anticipated procedures and allow safe creation of a tract. 3. Puncture below the 11th rib (and preferably below the 12th rib when feasible). 4. Puncture the tip of a posterior calix from a 20 degrees-30 degrees, posterolateral oblique approach to avoid major blood vessels. 5. Make a single-wall puncture of the calix. 6. Perform exchange transfusion for opacification of the renal pelvis and calices during percutaneous nephrostomy procedures to minimize the risk of sepsis. Overdistention can increase the likelihood of sepsis or retroperitoneal contamination. 7. Inject contrast material via a catheter placed over a wire to confirm the intracollecting system location of the entry. 8. Avoid unnecessary (complicated, prolonged) procedures in an infected, obstructed system. 9. Use only self-retaining drainage catheters to minimize the risk of inadvertent catheter dislodgment. 10. Create large-bore tracts with a balloon dilation system. By contrast, radiologists should not do the following: 1. Puncture above the 11th rib (unless all other avenues of approach have been exhausted). 2. Lose access to an obstructed kidney once the kidney has been punctured. Placement of a "safety" wire for all complex manipulations is recommended. 3. Panic if excessive bleeding or evidence of adjacent organ injury is seen. Excessive bleeding usually can be stopped with tract tamponade by using a balloon catheter advanced through the tract or with placement of an appropriate-sized nephrostomy tube to occlude the tract. If active bleeding continues or recurs, arteriography should be considered. The quantity of bleeding can be monitored with sequential hematocrit measurements. Almost all renal artery injuries can be treated with minimally invasive procedures, such as selective embolization of the branch artery involved, and this will lead to infarction of only a small segment of kidney, with preservation of functioning renal parenchyma. Injury to an adjacent organ usually can be treated nonsurgically (21,23). The most commonly injured extrarenal abdominal organ is the colon (Fig 6). On occasion, a percutaneous nephrostomy needle may traverse the retroperitoneal segment of the colon, and this type of injury generally can be treated nonsurgically, as well (23). If the colon has been traversed, adequate urinary drainage should be ensured before the transcolonic nephrostomy catheter is removed (so that a nephrocolonic fistula is not maintained). This can be done by placing a ureteral stent and a bladder catheter (18). Once adequate urinary drainage is provided, the nephrostomy catheter can be withdrawn into the colon and used as a percutaneous colostomy drain. The percutaneous colostomy tract should be allowed to mature for several days before this catheter is removed. In addition, appropriate antibiotics should be administered from the time a transcolonic tract is identified until the percutaneous tract has healed completely. Transthoracic entry can cause pneumothorax and pleural effusions. These should be treated only if they are large or cause symptoms (21). (ABSTRACT TRUNCATED)

Gender-related differences in expression of murine glutathione S-transferases and their induction by butylated hydroxyanisole.

The basal levels of mu and pi class glutathione S-transferases RNA were 18-fold higher in the male mouse liver as compared with the female. When 0.75% (w/w) BHA was included in the diet it altered the RNA levels of alpha, mu, pi GST classes and mGSTA4-4 in a tissue and sex specific manner. The most marked induction of RNA was seen for the mu class GSTs of female liver, lung and kidney (52, 10 and 8-fold, respectively), and of male liver and kidney (25 and 3.5-fold, respectively), the pi class GSTs of female liver, lung, and kidney (11, 10, and 5-fold, respectively), and mGSTA4-4 of female liver (4-fold). The effect of BHA on the induction of the mu and pi class GST RNA was 2-9 fold greater in female as compared with male tissues. The degree of induction of GST RNA did not correlate directly with changes in GST protein indicating that post-transcriptional events regulating GST expression may be affected by BHA particularly for GST mu and mGSTA4-4.

CT diagnosis of acute flank pain from urolithiasis.

The use of noncontrast helical CT (NHCT) to assess patients with acute flank pain and hematuria for potential urinary tract stone disease was first reported in 1995. After several years of experience with the technique, sensitivity and specificity of NHCT has proven to be better than intravenous urography for evaluating ureteral stones. NHCT imaging findings for urinary calculi and the differential diagnosis are discussed in this article. Various extraurinary diseases found while using NHCT in searching for stone disease are addressed and illustrated. As experience with the use of NHCT has increased, clinicians have broadened the indications for this technique, which has a lower charge than standard CT, beyond the specific evaluation of urinary colic. This indication creep has increased the number of NHCT examinations ordered. It has also reduced the rate of stone positivity and increased the diagnostic yield for extraurinary disease.

Radiologic findings in acute urinary tract obstruction.

Acute urinary tract obstruction, a common disease in daily practice, often requires performance of emergency intravenous urography (IVU). However, the spectrum of urographic abnormalities seen with acute obstruction has not been thoroughly addressed. The purpose of this study was to explore the IVU findings in patients with acute urinary tract obstruction. Records of 380 patients who underwent IVU in our hospital during a 6-mo period were reviewed for IVU evidence of acute urinary tract obstruction. Of the 380 patients, 53 (14%; 39 men, 14 women; average age = 43 yr) had acute urinary tract obstruction. All obstructions except one were located in the lower one-third of the ureter. The causes of acute urinary obstruction included ureteral stones in 34 (64%), ureteral edema or lucent stones in 16 (30%), neoplasms in 2 (4%), and inflammatory disease in 1 (2%). Abnormal radiologic findings were hydroureter in 46, nephropyelographic delay in 36, hydronephrosis in 35, interureteric ridge edema in 11, persistent dense nephrogram in 6, urine extravasation in 5, vicarious excretion in 1, striation in 1, and stricture in 1. Radiographic results were normal in one patient. The most common clinical indications of acute ureteral obstruction are flank pain and hematuria, and calculi are the major cause. In one-third of patients, radiopaque calculi are not detectable with IVU during acute urinary tract obstruction. A careful and thorough evaluation of the IVU should be performed in patients with clinical indications of acute urinary obstruction.

False-positive radionuclide hepatobiliary imaging following cystic duct stone removal.

The authors report a case in which a radionuclide hepatobiliary image was falsely indicative of cystic duct obstruction in a patient with an indwelling cholecystostomy tube and an externalized gallbladder-duodenal stent. Cystic duct patency was demonstrated radiographically shortly before and after the radionuclide study. The authors recommend that cystic duct obstruction indicated by a radionuclide hepatobiliary image be confirmed by another means if a cholecystostomy tube is present, or if the patient recently has undergone percutaneous gallbladder or cystic duct manipulations.

Mass effect in the renal sinus: an anatomic classification.

Before the advent of modern imaging techniques, pathologic processes in the renal sinus were diagnostic enigmas. Many of the conditions create nonspecific deformities of the contrast-filled collecting system. In the past, the discovery of these abnormalities often led to unnecessary exploration. Modern imaging techniques usually allow a specific diagnosis to be made, but because a number of the pathologic conditions affecting the renal sinus have similar appearances on a single type of imaging study, complete delineation may require correlation of a number of diagnostic techniques. An understanding of the normal sinus anatomy allows classification of pathologic processes that occur in this region and ensures an orderly imaging investigation. The anatomic classification is based on the structure from which the mass arises. The source of the mass may be any structure within the renal sinus (intrinsic), the enveloping renal parenchymal (adjacent), or a source outside the kidney itself with subsequent sinus involvement (extrinsic). This classification will be used to review a number of pathologic processes that occur in the renal sinus and pertinent imaging features.

Locating the kidneys on CT to guide nephrotomography.

Tomography of the kidneys is a routine procedure performed during intravenous urography. Precisely locating the kidneys, however, can be difficult. This article describes a study performed to determine a simple and accurate measurement for kidney location as a guide to obtaining initial nephrotomographic sections. The authors measured the distance from the midplane of the kidney to the posterior skin line on abdominal CT images in 26 patients. This distance averaged one-third the thickness of the abdominal region. The best depth for the nephrotomographic cut was found to be one-third the thickness of the abdomen plus the thickness of any table pad.