Modulation of a glycoprotein recognition system on rat hepatic endothelial cells by glucose and diabetes mellitus.

The cellular location and carbohydrate specificities of a glycoprotein recognition system on rat hepatic sinusoidal cells have been determined. Purified preparations of endothelial, Kupffer, and parenchymal cells were prepared by collagenase liver perfusion, centrifugation on Percoll gradients, and centrifugal elutriation. (125)I-labeled agalactoorosomucoid, an N-acetylglucosamine-terminated glycoprotein, was selectively taken up in vitro by endothelial cells. Uptake was shown to be protein dependent, calcium ion dependent, and saturable, and could be described by Michaelis-Menten kinetics (apparent K(m) 0.29 muM; apparent maximum velocity 4.8 pmol/h per 5 x 10(6) cells). Uptake was inhibited not only by N-acetylglucosamine, mannose, and mannan but also by glucose, fructose, and a glucose-albumin conjugate. Inhibition by glucose was competitive over a wide range of concentrations and was almost 100% at a glucose concentration of 56 mM. Fasting and the induction of diabetes mellitus prior to isolation of cells was associated with 60% reductions in the recovery of endothelial cells. Uptake by cells isolated from fasted rats was enhanced (apparent maximum velocity 14.3 pmol/h per 5 x 10(6) cells without change in the apparent K(m)). These observations suggest that fasting is associated with a marked increase in the mean number of glycoprotein receptors per endothelial cell isolated from normal rats. This effect of fasting could be due to upregulation of glycoprotein receptors on endothelial cells or to the selective isolation of a subpopulation of endothelial cells from fasted animals that bears more glycoprotein receptors per cell than does another subpopulation of these cells. In addition, in vivo studies of the fate of intravenously administered (125)I-agalactoorosomucoid indicated that its rate of disappearance from plasma, hepatic accumulation, and catabolism were slower in diabetic than in normal rats. The results suggest that modulation of a carbohydrate-mediated glycoprotein recognition system located on hepatic endothelial cells can be induced by glucose and glucose-conjugated proteins and by fasting and diabetes mellitus. The findings in this study suggest a mechanism for abnormal glycoprotein metabolism in diabetes mellitus.

Carbohydrate-binding proteins of human serum: isolation of two mannose/fucose-specific lectins.

Two lectins with specificities for mannose and fucose have been isolated from human serum by affinity chromatography. One mannose-binding protein (MBP 1) has a native Mr of 700,000 with subunits of Mr 32,000 and has specificities for N-acetylglucosamine, N-acetylmannosamine and glucose as well as for mannose and fucose. The other mannose-binding protein (MBP 2) has a native Mr of 200,000 with subunits of Mr 28,000 and is specific only for mannose and fucose. MBP 2 appears to recognize the core sugars of asparagine-linked oligosaccharides as well as the terminal sugars. Both lectins are calcium-dependent, requiring approx. 0.095 mM calcium for half-maximal binding. MBP 1 binds maximally between pH 7-9, whereas MBP 2 has a pH optimum of 6-7. The binding activity of both proteins decreases rapidly below pH 5. The apparent association constants (Ka) for binding to mannon are 2.1 X 10(8) M-1 for MBP 1 and 1.3 X 10(8) M-1 for MBP 2. These data provide further evidence of the complex nature of mammalian carbohydrate recognition systems.

Mannose-binding proteins in human serum: identification of mannose-specific immunoglobulins and a calcium-dependent lectin, of broader carbohydrate specificity, secreted by hepatocytes.

Human serum contains lectins which inhibit the uptake of mannose- and N-acetylglucosamine-terminated glycoproteins by isolated rat hepatic sinusoidal cells. In these experiments, calcium-dependent and calcium-independent human serum mannose-binding proteins have been isolated by affinity chromatography using mannan linked to four different supports. In electroblots both calcium-dependent and -independent serum mannose-binding proteins bound radioiodinated mannan and invertase in the presence of calcium ions, but the binding of calcium-dependent serum mannose-binding proteins was abolished by EDTA. Chicken antibodies were raised against serum mannose-binding proteins and an ELISA was developed. The principal calcium-independent serum mannose-binding protein is mannose-specific IgG as judged by immunodiffusion and electroblotting with anti-human IgG antibodies. The calcium-dependent serum mannose-binding protein is probably the secreted form of an intracellular hepatocyte mannose-binding protein since: antibodies raised against the 30 kDa subunit of the calcium-dependent serum mannose-binding protein also bound 30 kDa subunits of whole liver homogenate and purified human liver mannose-binding protein; antibodies to the human liver mannose-binding protein bound to the 30 kDa subunit of the calcium-dependent serum mannose-binding protein; and the binding specificities of the calcium-dependent serum mannose-binding protein for N-acetylglucosamine and fucose as well as mannose, and its recognition of the core region of an oligosaccharide rather than only the peripheral sugars, were identical to those reported for the hepatocyte mannose-binding protein. The physiological ligands of these serum mannose-binding proteins are unknown but they could bind noxious glycoproteins which enter the circulation prior to their removal by the sinusoidal mannose receptor.

Mutations in the human mannose-binding protein gene: frequencies in several population groups.

Mannose-binding protein (MBP; mannan-binding protein, mannan-binding lectin) is a member of the collectin family of proteins and is thought to be important in innate immunity. We have previously shown high frequencies of two distinct mutations in codon 54 and codon 57 of exon 1 of the MBP gene in non-African and African populations, respectively. These result in low levels of the protein and an opsonic deficiency but the frequencies also suggest some selective advantage for low MBP levels. A third mutation in codon 52 occurs at a much lower frequency. We have now extended our earlier studies to other populations. In the south-west Pacific (Papua New Guinea and Vanuatu) neither the codon 52 nor the codon 57 mutation was detected and the codon 54 mutation was significantly less common (gene frequencies of 0.07 and 0.01, respectively) than in other non-African populations (gene frequencies 0.11-0.16). This could be explained by relatively recent admixture. The ancestral Melanesian population probably diverged some 50,000-60,000 years ago and our data suggest that the codon 54 mutation may have occurred after that even but before the divergence of European-Asian groups (40,000 years ago). Two further sub-Saharan populations were also studied: a group of Xhosa from South Africa were similar to Gambians, with a high gene frequency for the codon 57 mutation (0.27) and no evidence of the codon 52 or 54 mutations. In contrast, San Bushmen from Namibia had low frequencies of both the codon 57 mutation (0.07) and the codon 54 mutation (0.03). Again the codon 52 mutation was not found. This pattern is unique amongst sub-Saharan populations studied to date and suggests that this population may have been subjected to different selective pressures.

Human serum contains a lectin which inhibits hepatic uptake of glycoproteins.

Human serum will inhibit the specific uptake of N-acetylglucosamine-terminated glycoproteins by isolated rat hepatic sinusoidal cells. The serum inhibitors are not glycoproteins that bind to the hepatic mannose/N-acetylglucosamine receptor but have the properties of lectins which bind to mannose/N-acetylglucosamine-terminated glycoproteins. They can be isolated from serum by affinity chromatography. The predominant lectin, with a molecular mass of less than 35 kDa, will inhibit the sinusoidal cell uptake of glycoproteins in vitro.

Identical point mutation leading to low levels of mannose binding protein and poor C3b mediated opsonisation in Chinese and Caucasian populations.

A common opsonic defect occurring in 7% of the Caucasian population is associated with low serum levels of the lectin mannose binding protein (MBP). This study sought to determine whether the deficiency was also present in a Chinese population using sera obtained from 100 healthy Chinese children (age range 6 weeks-16 years). The distribution profiles of MBP levels and C3b/C3bi fragments binding to mannan coated plates were both bimodal and similar to the corresponding Caucasian profiles. Serum MBP levels were low in 9% of the Chinese children and all of these sera generated low levels of C3b/C3bi fragments. Overall there was a high significant correlation between MBP levels and C3b opsonin generation (r = 0.77; P less than 0.001). By analogy with similar findings in a Caucasian population we believe this correlation to be a reflection of antibody independent complement activation by MBP. In a pilot study of DNA obtained from three adult Chinese with low MBP levels the point mutation causing MBP deficiency in Caucasians was identified in all three cases.

Review article: dissolution of gallstones in the biliary tree.

There are a variety of methods for dissolving gallstones in the biliary tree, which include oral therapy and direct contact dissolution. Cholesterol gallstones are most amenable to dissolution. Developments in non-operative physical methods to remove gallstones (particularly endoscopic papillotomy and extracorporeal shock-wave lithotripsy have diminished the use of chemical dissolution. However, in selected patients, there remains a place for chemical dissolution, but often in conjunction with the physical techniques.

Serum immunoreactive trypsin concentration after a Lundh meal. Its value in the diagnosis of pancreatic disease.

The changes in serum trypsin concentration have been measured in 47 subjects for up to 2 hours after a Lundh meal. In 18 healthy controls, mean fasting trypsin concentration was 285 +/- 125 ng/ml (mean +/- 2 SD). The maximum increase after the Lundh meal (the trypsin response ratio) was 6.7 +/- 7.5%. Six patients with chronic renal failure had elevated fasting serum trypsin concentrations (range 460-1100 ng/ml) but trypsin response ratios fell within the control range. Of five patients with relapsing pancreatitis, two had raised and three normal or low fasting trypsins. After stimulation two had elevated trypsin response ratios; one of the two had evidence of main duct obstruction. Eleven out of 12 patients with chronic pancreatitis (with or without insufficiency) had low fasting trypsin concentrations (range 0-120 ng/ml) Seven of the 12 also had raised trypsin response ratios. In six patients with cancer of the pancreas, fasting trypsin was low in three, normal in two, and raised in one. Both patients with a normal fasting level had a raised trypsin response ratio. The combination of a single estimation of fasting serum trypsin concentration followed by serial measurements after a Lundh meal provides a useful screening test for chronic pancreatic disease.

Combined percutaneous transhepatic and endoscopic placement of biliary stents.

Combined percutaneous transhepatic cholangiography and endoscopic retrograde cholangiography can be used to stent biliary obstruction when attempts at endoscopic stenting have failed. Between January 1987 and August 1991 we performed 35 combined procedures in 31 patients with malignant obstruction. Post stenting serum bilirubin and serum alkaline phosphatase concentration fell after 33 and 29 procedures, respectively. In six studies there was evidence of infection prior to stenting. In spite of the use of prophylactic antibiotics, septic complications developed after eight procedures (23%). Pseudomonas was the most commonly isolated pathogen (46%). Twenty-three patients were discharged, 30-day mortality was 8 (23%) and median survival was 14 weeks (range 0-75 weeks). Seven patients required eight stent changes because of blockage (median patency time 18 weeks; range 7-75 weeks). Use of this technique allows relief of biliary obstruction. Potential infective and bleeding complications must be anticipated.

The effect of an acute phase reaction and BCG innoculation on factor VIII in the guinea-pig.

Factor VIII antigen (VIII:Ag) and vWF:Antigen (vWF:Ag) were measured in guinea-pigs treated with intraperitoneal turpentine to induce an acute phase reaction, and with BCG to stimulate the reticulo-endothelial system. In the turpentine treated animals there was a significant rise of fibrinogen at 24 and 48 hours after injection (1.43 +/- 0.01 g/l) when compared with controls (1.15 +/- 0.1 g/l), mean +/- SEM n = 3 p 0.01). There was no change in plasma VIII:Ag but a significant rise of vWF:Ag at (2.0 +/- .3 units/ml) when compared with controls (1.1 +/- 0.05 units/ml, mean +/- SEM n = 3 p less than 0.001). Examination of perfused guinea-pig organs showed a reduction in hepatic VIII:Ag (82%) and vWF:Ag (90%) and a 76% increase in splenic vWF:Ag only in the turpentine treated animals. Distribution of 125I Albumin to detect trapped blood in tissues demonstrated efficient clearance of blood by perfusion. There was no change in the plasma concentration of either VIII:Ag or vWF:Ag following BCG inoculation but there was a 45% increase in the splenic concentration of vWF:Ag. It is concluded that only the factor vWF:Ag and not the factor VIII:Ag component of the factor VIII complex is an acute phase reactant in guinea-pig and that this may be due to increased synthesis of vWF:Ag by vascular endothelium in the spleen. Although BCG inoculation may have stimulated synthesis or storage of vWF:Ag in the spleen it did not have an appreciable effect on the plasma concentration of either VIII:Ag or vWF:Ag.

Basement membrane proteins and type III procollagen in murine schistosomiasis.

The livers of female CBA mice were examined 9 to 10 weeks after subcutaneous infection with Schistosoma mansoni. Cryostat liver sections and isolated liver cells were examined by indirect immunofluorescence using specific antibodies against basement membrane proteins (laminin, fibronectin and type IV collagen and type III collagen precursor. Liver cells were isolated by collagenase digestion, purification on Percoll density gradients and centrifugal elutriation to yield enriched fractions of hepatocytes, endothelial and Kupffer cells (Fractions I, II, III respectively). Infected animals yielded more than three times the control number of non-parenchymal cells; electron microscopy revealed that the increase in Fraction II was due mainly to eosinophilic leucocytes and in Fraction III due to Kupffer cells and macrophages from the schistosomal granulomata. Studies of cryostat liver sections showed that the schistosomal granulomata contained dense deposits of type III collagen precursor and fibronectin in the distribution of the reticulin fibres but laminin and type IV collagen were conspicuous only in new vessels in the periphery of the granuloma. Isolated liver cells showed fibronectin on their surface. Immunofluorescence studies could not be performed on Kupffer and endothelial cell fractions because of marked non-specific fluorescence. These experiments indicate that centrifugal elutriation is a useful method for isolating the constituent cells of murine schistosomal granulomata.

Endoscopic sphincterotomy for bile duct stones.

This paper reports the results of endoscopic sphincterotomy for bile duct stones in 50 patients. A design for a spincterotomy handle and a suitable stainless steel diathermy wire are described. Sphincterotomy was achieved in 45 patients (90%) and complete stone clearance in 42 (84%); this usually required two endoscopic examinations. Complications occurred in nine patients. Haemorrhage and pancreatitis were the most serious resulting in one laparotomy (haemorrhage) and one death (pancreatitis). Periampullary diverticula in 11 patients (22%) did not influence the success rate or the frequency of complications. A "pre-cut" in 11 patients (22%) permitted a later successful sphincterotomy in eight. Stone size (up to 3.5 cm) did not appear to influence outcome, but complete stone clearance was only achieved in two out of eight with more than ten bile duct calculi. Symptoms have not recurred up to three years after sphincterotomy. The data indicate that endoscopic sphincterotomy is of major value in high-risk patients with bile duct calculi and is also appropriate for most low-risk patients with retained stones after cholecystectomy.

Mannose-binding protein in HIV-seropositive patients does not contribute to disease progression or bacterial infections.

This study set out to investigate whether plasma mannose-binding protein (MBP) deficiency caused by mutations in the MBP gene associates with pyogenic or opportunistic infections in HIV-infected patients. Plasma samples were selected randomly from 131 HIV-infected patients followed prospectively for a period not exceeding 12 months or until death. Plasma MBP concentrations were measured by an ELISA and genotyping was determined by amplification of exon 1 of the MBP gene by polymerase chain reaction (PCR) technology, followed by restriction enzyme analysis and Southern blotting using sequence-specific oligonucleotide probes. Neither MBP concentration nor genotype was found to associate with disease progression or opportunistic infection rate. There was an unexpected increased bacterial infection rate in patients with MBP levels greater than 100 ng/ml and wild type genotype. Thus, MBP does not appear to play a role in HIV infection. MBP is an acute phase reactant and this may explain the higher levels in those with more frequent pyogenic infections.

The decay of endogenously labelled 75Se-selenomethionine labelled proteins in duodenal juice: evidence for recirculation in man.

The decay of the specific radioactivity of duodenal juice proteins, endogenously labelled with 75Se-selenomethionine has been studied in man. Duodenal juice was collected against a background infusion of cholecystokinin-pancreozymin (1 unit/kg/hr) and secretin (1 unit/Kg/hr). In 4 subjects, duodenal juice was aspirated continuously and pooled in 30 min. aliquots. In 3 other subjects approximately 5-10 ml of juice was removed at 15 min, intervals. The rate of decay of protein specific radioactivity was significantly more rapid in the drainage group (p less than 0.01). A similar trend was also observed for trypsin. The data suggests that endogenous duodenal juice proteins might be recirculated as intact proteins in man.

A distinctive pattern of serum bile acid and bilirubin concentrations in benign recurrent intrahepatic cholestasis.

The pattern of serial serum bile acid and bilirubin concentrations in 3 patients with benign recurrent intrahepatic cholestasis (BRIC) was compared with those from patients with other liver diseases. In BRIC the peak bile acid concentration (260- 575 micromol/l was found at the onset of the cholestasis. The bilirubin concentration increased slowly so that maximum values (185-550 micromol/l) were attained between 33 and 51 days after the onset of symptoms. Both the serum bile acid and bilirubin concentrations returned to normal after 79 to 98 days. Percutaneous biliary drainage of extrahepatic biliary obstruction (3) caused a dramatic reduction in the serum bile acid level (mean 89% after 48 hours), but only a slight fall in serum bilirubin (mean 22%). In primary biliary cirrhosis (2) the bile acid and bilirubin concentrations changed in parallel until the onset of liver failure when serum bilirubin, but not bile acids, increased markedly. Serum bile acid and bilirubin concentrations changed in parallel throughout cholestatic viral hepatitis (2), chronic active hepatitis (2) and alcoholic hepatitis (1). The data indicates that a distinctive pattern is found in BRIC and this may be of diagnostic value.

Association of mutations in mannose binding protein gene with childhood infection in consecutive hospital series.

OBJECTIVE: To determine the extent to which mutations in the mannose binding protein gene predispose to childhood infection. DESIGN: Clinical details and genotype of mannose binding protein determined in consecutive children attending a paediatric department. SETTING: Inner city hospital paediatric service in London. SUBJECTS: 617 children attending hospital between October 1993 and August 1995. MAIN OUTCOME MEASURE: Infection as the cause for attendance or admission in relation to mutations in the mannose binding protein gene. RESULTS: The prevalence of mutations in the mannose binding protein gene in children with infection (146/345) was about twice that in children without infection (64/272) (P < 0.0001). Increased susceptibility to infection was found in both heterozygotic and homozygotic children. 13 out of 17 children homozygotic for variant alleles presented with strikingly severe infections, including 6 with septicaemia. CONCLUSIONS: The findings suggest that mutations in the mannose binding protein gene are an important risk factor for infections in children. Screening for such mutations should be included in the investigation of severe or frequent infections.

Medical treatment of gallstones.

The last 10 years have witnessed an enormous amount of work on the medical dissolution of gallstones. Many compounds have been tested and one, chenodeoxycholic acid, is already available for clinical use in the UK. Others will certainly follow. Much remains to be learned of the mechanisms of action of these drugs and the safety of prolonged administration. Effective methods of preventing gallstone recurrence need to be devised. The practice of cholecystectomy is not yet threatened by medical dissolution of gallstones, but in selected patients medical treatment is now a viable alternative. A start has been made.