Albinism in phylogenetically and geographically distinct populations of Astyanax cavefish arises through the same loss-of-function Oca2 allele.

The Mexican tetra, Astyanax mexicanus, comprises 29 populations of cave-adapted fish distributed across a vast karst region in northeastern Mexico. These populations have a complex evolutionary history, having descended from 'old' and 'young' ancestral surface-dwelling stocks that invaded the region ∼6.7 and ∼2.8 MYa, respectively. This study investigates a set of captive, pigmented Astyanax cavefish collected from the Micos cave locality in 1970, in which albinism appeared over the past two decades. We combined novel coloration analyses, coding sequence comparisons and mRNA expression level studies to investigate the origin of albinism in captive-bred Micos cavefish. We discovered that albino Micos cavefish harbor two copies of a loss-of-function ocular and cutaneous albinism type II (Oca2) allele previously identified in the geographically distant Pachón cave population. This result suggests that phylogenetically young Micos cavefish and phylogenetically old Pachón cave fish inherited this Oca2 allele from the ancestral surface-dwelling taxon. This likely resulted from the presence of the loss-of-function Oca2 haplotype in the 'young' ancestral surface-dwelling stock that colonized the Micos cave and also introgressed into the ancient Pachón cave population. The appearance of albinism in captive Micos cavefish, caused by the same loss-of-function allele present in Pachón cavefish, implies that geographically and phylogenetically distinct cave populations can evolve the same troglomorphic phenotype from standing genetic variation present in the ancestral taxon.

Effects of aldosterone and potassium-sparing diuretics on electrical potential differences across the distal nephron.

We have previously shown that the transtubular potential of the rabbit cortical collecting tubule varies in concert with changes in plasma mineralocorticoid levels, while the potential of the distal convoluted tubule is invariant with such changes. In the present studies we have examined the effects of in vitro addition of d-aldosterone to isolated tubules, as well as the effects of triamterene and spirolactone. d-Aldosterone (0.2 mum added to the perfusate or 1 muM added to the bathing medium) resulted in a marked stimulation of the transtubular potential difference (lumen-negative) after a short latent period. d-Aldosterone had no effect on the potential difference of distal convoluted tubules of intact or adrenalectomized rabbits. Both the magnitude of the response and the length of the latent period in the cortical collecting tubule after aldosterone were markedly temperature-dependent. Triamterene caused a gradual but reversible inhibition of the potential difference in the cortical collecting tubule but had no effect in the distal tubule. Spirolactone, when added before aldosterone, blocked the electrical response to the hormone in the cortical collecting tubule, and produced a gradual inhibition of the potential difference in mineralocorticoid-stimulated tubules. Spirolactone had no effect on the potential difference of the distal tubule. We conclude that (a) the influence of aldosterone on the potential across the distal nephron is restricted to the distal convoluted tubule, (b) the electrical response to aldosterone and the latent period are temperature-dependent, (c) the response to aldosterone is blocked by spirolactone, and (d) triamterene inhibits the potential difference only in the cortical collecting tubule.

A functional comparison of the cortical collecting tubule and the distal convoluted tubule.

Electrical and permeability features of the distal convoluted tubule (DCT) and the cortical collecting tubule (CCT) were examined using the technique in which isolated segments of rabbit tubules were perfused in vitro. When rabbits were given a regular diet and tubules were perfused and bathed in artificial solutions simulating plasma ultrafiltrate, the potential difference (PD) was +3.7 plus or minus 1.9 mV in the CCT and -40.4 plus or minus 2.8 mV in the DCT. When rabbits were given a low sodium, high potassium diet plus i.m. deoxycorticosterone acetate (DOCA) (1 mg/kg per day), the PD in both the CCT (-30.8 plus or minus 3.9 mV) and the DCT (-33.8 plus or minus 5.5 mV) was negative. The PD in the CCT was quantitatively similar to that of diet plus DOCA when animals were given DOCA alone. The PD in both segments was inhibited by ouabain (10-minus 5 M) in the bath or by amiloride (10-minus 5 M) in the perfusate. Addition of vasopressin (200 muU/ml) to the bath caused a gradual decline of PD to zero in the CCT but failed to produce a potential response in the DCT. Osmotic water permeability was essentially zero in both segments in the absence of vasopressin. After addition of the vasopressin to the bath, osmotic water permeability in the DCT remained zero but increased to 71.9 plus or minus 25.5 X 10-minus 7 cm/s per atm in the CCT. We conclude that both segments are similar in that each possesses an electrogenic transport process but that these segments differ in that: (a) the CCT requires either exogenous or endogenous mineralocorticoid to maintain a maximal negative PD, whereas the PD in the DCT appears to be independent of mineralocorticoid effect; and (b) the CCT responds to vasopressin with a marked rise in water permeability, whereas the DCT is impermeable to water before and after addition of vasopressin.

Electrophysiological study of isolated perfused human collecting ducts: Ion dependency of the transepithelial potential difference.

Cortical and outer medullary collecting duct segments were dissected from human kidneys and perfused in vitro. The transepithelial potential difference was measured and found to be lumen positive +6.8 +/- 0.6 mV (n= 20). This lumen-positive potential difference was inhibited by ouabain and furosemide but not by acetazolamide. Replacement of chloride in bath and perfusion fluids caused a reversible decrease of the potential difference to near zero. We conclude from these studies: (a) the lumen-positive potential difference is dependent upon the presence of chloride ion suggesting the existence of an active electrogenic chloride reabsorptive process in the human collecting duct and (b) it is possible to examine human renal physiology directly using in vitro microperfusion of tubule segments.

Biliary copper excretion by hepatocyte lysosomes in the rat. Major excretory pathway in experimental copper overload.

We investigated the hypothesis that lysosomes are the main source of biliary copper in conditions of hepatic copper overload. We used a rat model of oral copper loading and studied the relationship between the biliary output of copper and lysosomal hydrolases. Male Sprague-Dawley rats were given tap water with or without 0.125% copper acetate for up to 36 wk. Copper loading produced a 23-fold increase in the hepatic copper concentration and a 30-65% increase in hepatic lysosomal enzyme activity. Acid phosphatase histochemistry showed that copper-loaded livers contained an increased number of hepatocyte lysosomes; increased copper concentration of these organelles was confirmed directly by both x ray microanalysis and tissue fractionation. The copper-loaded rats showed a 16-fold increase in biliary copper output and a 50-300% increase in biliary lysosomal enzyme output. In the basal state, excretory profiles over time were similar for biliary outputs of lysosomal enzymes and copper in the copper-loaded animals but not in controls. After pharmacologic stimulation of lysosomal exocytosis, biliary outputs of copper and lysosomal hydrolases in the copper-loaded animals remained coupled: injection of colchicine or vinblastine produced an acute rise in the biliary output of both lysosomal enzymes and copper to 150-250% of baseline rates. After these same drugs, control animals showed only the expected increase in lysosomal enzyme output without a corresponding increase in copper output. We conclude that the hepatocyte responds to an increased copper load by sequestering excess copper in an increased number of lysosomes that then empty their contents directly into bile. The results provide direct evidence that exocytosis of lysosomal contents into biliary canaliculi is the major mechanism for biliary copper excretion in hepatic copper overload.

Advantages of external hybrid fixators for treating Schatzker V-VI tibial plateau fractures: A retrospective study of 40 cases.

INTRODUCTION: Proximal tibia fractures make up 1% of all fractures in adults. The fractures classified as Schatzker V and VI fractures can compromise knee structure and function. They are challenging to treat and often have complications. While plate fixation is the gold standard, the resulting infection rate has led us to favor external hybrid fixation. The aims of this study were to assess the radiographic and functional outcomes along with the complication rate when using this method and to compare them to historical plate fixation data. MATERIAL AND METHODS: This was a retrospective study of 40 patients. The complications, quality of reduction, IKS, Lysholm and Rasmussen functional scores at the latest follow-up and factors affecting the functional outcome were evaluated. These parameters were compared to published results from plate fixation studies. RESULTS: The deep infection rate was 2.5%. The union rate was 80%. Satisfactory reduction was obtained in 70% of cases; however, 52% of patients had malunion. The mean IKS score was 73.74, the mean Rasmussen score was 22.85 and the mean Lysholm score was 75.53. Age, reduction at latest follow-up, mechanical axis and anteroposterior laxity had a significant effect on the functional outcome. DISCUSSION: Despite the malunion rate being higher than other studies, the functional outcomes were nearly identical based on the variables measured. There are several advantages associated with using a hybrid external fixator: shorter operative time, less bleeding, shorter hospital stays and lower infection rate. CONCLUSION: Hybrid external fixation is a reliable fracture fixation method that leads to satisfactory functional outcomes, while reducing the infection rate and allowing arthroplasty to be performed in the future if needed.

Accuracy and reproducibility of preoperative three-dimensional planning for total hip arthroplasty using biplanar low-dose radiographs : A pilot study.

BACKGROUND: In total hip arthroplasty (THA), the acetabular cup and femoral stem must be correctly sized and positioned to avoid intraoperative and postoperative complications, achieve good functional outcomes and ensure long-term survival. Current two-dimensional (2D) techniques do not provide sufficient accuracy, while low-dose biplanar X-rays (EOS) had not been assessed in this indication. Therefore, we performed a case-control study to : (1) evaluate the prediction of stem and cup size for a new 3D planning technique (stereoradiographic imaging plus 3D modeling) in comparison to 2D templating on film radiographs and (2) evaluate the accuracy and reproducibility of this 3D technique for preoperative THA planning. HYPOTHESIS: Accuracy and reproducibility are better with the 3D vs. 2D method. PATIENTS AND METHODS: Stem and cup sizes were retrospectively determined by two senior surgeons, twice, for a total of 31 unilateral primary THA patients in this pilot study, using 3D preplanning software on low-dose biplanar X-rays and with 2D templating on conventional anteroposterior (AP) film radiographs. Patients with a modular neck or dual-mobility prosthesis were excluded. All patients but one had primary osteoarthritis; one following trauma did not have a cup implanted. The retrospectively planned sizes were compared to the sizes selected during surgery, and intraclass coefficients (ICC) calculated. RESULTS: 3D planning predicted stem size more accurately than 2D templating: stem sizes were planned within one size in 26/31 (84%) of cases in 3D versus 21/31 (68%) in 2D (P=0.04). 3D and 2D planning accuracies were not significantly different for cup size: cup sizes were planned within one size in 28/30 (92%) of cases in 3D versus 26/30 (87%) in 2D (P=0.30). ICC for stem size were 0.88 vs. 0.91 for 3D and 2D, respectively. Inter-operator ICCs for cup size were 0.84 vs. 0.71, respectively. Repetitions of the 3D planning were within one size (except one stem), with the majority predicting the same size. DISCUSSION: Increased accuracy in 3D may be due to the use of actual size (non-magnified) images, and judging fit on AP and lateral images simultaneously. Results for other implant components may differ from those presented. Size selection may improve further with planning experience, based on a feedback loop between planning and surgical execution. LEVEL OF EVIDENCE: Level III. Retrospective case-control study.

Non-responders to previous treatment for hepatitis C.

The main principle in treating chronic hepatitis C is the prevention of serious liver complications. Because curing hepatitis C virus infection has been demonstrated to prevent progression of liver disease and even promote regression of fibrosis, it remains the primary goal of treatment. However, nearly half of patients are not cured with our best treatment. Patients who failed older therapies should be treated with peginterferon and ribavirin, but those with advanced fibrosis or African heritage will have very low rates of response. Non-responders to peginterferon and ribavirin present a special challenge. If there were problems related to dosing, adherence, or access during treatment, then one can consider re-treating with the same regimen if the problems can be corrected. Otherwise, non-responders with early-stage fibrosis can observe without further treatment until newer drugs are available. Those with advanced fibrosis should consider low-dose peginterferon maintenance treatment or participation in an experimental trial. Experimental approaches include intensification of existing therapies, combination of new agents with existing drugs, long-term virus suppression, inhibition of liver fibrogenesis, and inhibition of hepatitis C RNA or hepatitis C viral enzymes.

Relationship between hepatitis C genotype and severity of recurrent hepatitis C after liver transplantation.

BACKGROUND: Recurrence of hepatitis C virus (HCV) infection after liver transplantation is universal, but the relationship between hepatitis C genotype and posttransplant outcome has been controversial. The aim of this study was to assess the relationship between hepatitis C genotype on posttransplant frequency of recurrent hepatitis, histologic severity of recurrence, and progression to cirrhosis. METHODS: We studied 42 HCV RNA positive patients who received transplants between 1985 and 1994. Sera were tested for HCV RNA and protocol liver biopsies were in obtained the posttransplant period. Biopsies were scored according to the histologic activity index (HAI) and staged in a blinded fashion. RESULTS: The distribution of hepatitis C genotypes distribution was as follows: 1a, 19 (45%); 1b, 17 (40%); 2b, 3 (7%); and 1 each of 2a, 3a, and 4a. There was histologic evidence of hepatitis in 38 of 42 (90.4%) of patients. Hepatitis C was mild, moderate, or severe (HAI>3) in 38% of grafts and minimal (HAI 0-3) in 62%. Overall HAI scores and histologic stage were higher in the genotype 1b group. Six of 17 (35%) genotype 1b patients had cirrhosis compared with 2 of 25 (8%) in the non-1b genotype group. CONCLUSIONS: (1) Histologic evidence of recurrent hepatitis C is seen in 90% of liver allografts; (2) Histologic hepatitis C recurs with similar frequency in genotype 1b and non-1b recipients; (3) Genotype 1b is associated with more severe histologic disease recurrence than non-1b genotypes; (4) Genotype 1b appears to be associated with a higher degree of posttransplant fibrosis and cirrhosis than non-1b genotypes.

Hepatitis G virus infection in patients transplanted for cryptogenic cirrhosis: red flag or red herring?

BACKGROUND: The significance of hepatitis G (HGV) infection in liver transplant recipients is not known. We set out to determine the pre-orthotopic liver transplantation (OLT) prevalence, the pre- and postoperative viral titers of HGV, and the allograft histology in patients infected with HGV who underwent OLT for cryptogenic cirrhosis. METHODS: HGV RNA was measured using a research-based branched DNA assay. The assay used a target-specific probe set that was based on the 5'-untranslated region of the HGV genome. Allograft histology was assessed with protocol liver biopsies in all patients who survived longer than 6 months. RESULTS: The preoperative prevalence of HGV infection in recipients transplanted for cryptogenic cirrhosis was 26%. Thirty-seven percent (12 of 33) of recipients who had serum available in the first postoperative month had HGV infection. Mean HGV RNA levels were 9.8 (+/-4.2) (viral molecular equivalents/ml x 10[6]) before OLT and 37.5 (+/-10.7) at 1 year after OLT. In 4 of the 11 cryptogenic recipients in whom HGV RNA was detectable in the first postoperative month, HGV RNA fell to undetectable levels at the most recent follow-up (mean 70 months). Of the five cryptogenic recipients who continue to have measurable HGV RNA, three have unexplained hepatitis histologically. CONCLUSIONS: These findings suggest the following: 1) The prevalence of HGV infection in patients undergoing OLT for cryptogenic cirrhosis is about 25%. 2) In recipients persistently infected with HGV, mean HGV RNA titers increase after OLT. 3) HGV RNA becomes undetectable in about one third of recipients who had detectable HGV RNA in the first month after OLT. 4) Hepatitis of uncertain etiology occurs in 60% (3 of 5) of persistently HGV-infected cryptogenic recipients.

Clinician's guide to hepatitis C.

Hepatitis C virus infection is common, often silent, and almost always chronic and can lead to cirrhosis and hepatocellular cancer. Deaths related to chronic hepatitis C are expected to increase dramatically in the future. Many cases of infection are asymptomatic and are undiagnosed because of a lack of recognition by patients and physicians. All patients currently or previously at risk of infection should undergo screening, including those who received blood transfusions before 1992. Interferon is the only effective therapy, but disappearance of virus is sustained in only 10 to 15% of patients. The combination of interferon and oral ribavirin therapy may increase the sustained response rate to about 40%. New agents such as hepatitis C virus-specific protease inhibitors may be available in the next 5 to 10 years, and treatment is evolving toward multiple-drug regimens analogous to those used for human immunodeficiency virus (HIV) infection. In contrast to public funding for drug development in HIV, such funding for hepatitis C has been limited.

Wilson's disease (hepatolenticular degeneration) of late adult onset: report of case.

Wilson's disease usually has its onset in childhood, adolescence, or early adulthood. The clinical picture of hepatic dysfunction without dysfunction of the central nervous system is more typical of the disease in the child or the adolescent than in the adult. We are presenting the case of a man whose age at onset of the disease was 55 years and who had the hepatic complications of Wilson's disease without clinical evidence of disease of the central nervous system. All patients with chronic hepatitis (chronic active liver disease) or cirrhosis of unknown etiology should be screened for the possibility of Wilson's disease. This screening should include slit-lamp biomicroscopy for Kayser-Fleischer rings, determination of serum ceruloplasmin concentration, and measurement of 24-hour urinary excretion of copper. If doubt exists concerning the diagnosis, either a radiocopper kinetic study, using 64Cu or 67Cu, or, if the patient's condition permits, a liver biopsy with measurement of hepatic copper concentration should be done. The rubeanic stain of hepatic tissue for copper is unreliable in making or excluding the diagnosis of Wilson's disease.

Hepatic cyst infection in autosomal dominant polycystic kidney disease.

To characterize the syndrome of hepatic cyst infection in autosomal dominant polycystic kidney disease (ADPKD) and to review its diagnosis and management, we retrospectively studied five such cases in patients from our institution and nine detailed case reports from the literature. The clinical manifestations were an acute (58%) or subacute (42%) febrile illness, typically associated with tenderness in the right upper quadrant, leukocytosis, a very high erythrocyte sedimentation rate, but minor abnormalities of liver function tests. Bacteremia was present in 7 of 11 patients. Enterobacteriaceae grew in pure culture from the cyst fluid in 9 of 12 patients. Complex cysts were observed by ultrasonography (in four of eight patients), computed tomography (in six of nine), and magnetic resonance imaging (in two of two). 111In leukocyte scans were positive in all four patients in whom they were done, and 67Ga scans were positive in only one of three patients. An unfavorable outcome was observed in six of seven patients treated with only antibiotics, in contrast with one of seven patients who received antibiotics and early drainage. In two patients, ciprofloxacin cyst levels were 2.3 and 4.8 times higher than the level in serum; in a third patient, cyst levels remained in therapeutic range 30 hours after the last dose of ciprofloxacin, at which time serum levels were undetectable. Clinical and laboratory features and the use of modern scanning techniques facilitate a prompt diagnosis of infection in hepatic cysts in ADPKD. The treatment of choice is a combination of percutaneous drainage and antimicrobial therapy.

Acute hepatic failure: the emerging role of orthotopic liver transplantation.

From 1985 through 1987, we diagnosed acute hepatic failure in 13 patients. Spontaneous recovery occurred in three of these patients. Eight patients underwent liver transplantation, five of whom survived and three of whom died. In addition, two patients died before undergoing transplantation. The survival rate of 62% was better than that among our previous series of similar patients. This improvement seems to be related to the use of orthotopic liver transplantation as a therapeutic alternative among these patients. One of the three patients who died after liver transplantation had normal liver function, but respiratory failure caused by Pneumocystis carinii developed 4 months after the transplantation. The surgical procedure was less difficult in patients with acute fulminant hepatitis than in those with chronic liver disease because fewer problems arose from adhesions, venous collaterals, and ascites. The emerging role of orthotopic liver transplantation in patients with acute hepatic failure is demonstrated by the improvement of survival rates observed by various groups, including ours, when this therapeutic modality is available.

Persistent centrilobular necroses in hepatic allografts.

A biopsy study of 60 allografts from 53 patients after orthotopic liver transplantation (OLT) revealed prominent centrilobular necrosis (CN) in 18% of the grafts that were suitable for analysis. The lesions often had a "punched-out" appearance, sometimes with unusual features such as giant cell formation. Persistent CN developed 4 weeks to 6 months after OLT, and persisted in two cases for 2 years and longer. In some instances, CN disappeared or healed by scarring. We found no association between CN and rejection arteritis or arteriopathy. Ductopenic (chronic) rejection subsequently occurred in six of eight livers with CN. Overall, patients with persistent CN had a worse prognosis than control patients. A comparison of cases with matched controls failed to reveal significant differences with respect to perioperative factors such as ischemia time, immunologic test results such as lymphocyte crossmatches, drug administration--in particular, of azathioprine, frequency of cellular (acute) rejection or infection episodes, or frequency of complications affecting major hepatic vessels or bile ducts. Morphologic evidence suggests that in some instances, rejection-induced endotheliitis/phlebitis of hepatic vein branches may lead to sinusoidal outflow blockage, sinusoidal dilatation, and dropout of hepatic cell plates. Although potentially reversible conditions such as ischemia or adverse drug reactions are among the possible causes of CN, severe rejection leading to ductopenia appears to be the most important underlying condition. Thus, presence of CN in repeated biopsy specimens from allografts should be considered a warning sign of irreversible rejection.

Chronic alcohol abuse and the acute sedative and neurophysiologic effects of midazolam.

The aim of the present investigation was to examine benzodiazepine sensitivity in abstinent alcoholics. For this purpose, two escalating doses of the benzodiazepine midazolam were i.v. administered to nine alcohol-dependent patients after 2-3 weeks of abstinence and 12 healthy, non-alcoholic volunteers. A variety of dependent measures were examined, including the power spectrum of the resting electroencephalogram (EEG) and evoked EEG responses, saccadic eye movements, self-reported sedation, and vigilance task performance. Analyses revealed a significant association between plasma midazolam levels and changes in EEG beta power, pattern shift visual evoked potential amplitude, heart rate, and saccade amplitude and velocity. The patient and control groups differed significantly in the onset latencies of their saccadic eye movements, and marginally in EEG beta power, both before and after midazolam. However, no differences were detected between the groups in the dose of midazolam required to produce sedation or in midazolam's neurophysiological effects.