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Biomedical subjects

L Backman

Publications and source records attributed to L Backman.

At least 127 records · Page 7Linked to original sources
PubMed1983

Urine composition following jejunoileal bypass.

The urinary excretion of oxalate, calcium, citrate, magnesium, urate and creatinine and the inhibition of calcium oxalate crystal growth were determined in 30 patients operated with three different types of jejunoileal bypass. In addition the ion-activity products of calcium oxalate and calcium oxalate saturation were calculated. 15 of the patients had formed urolithiasis postoperatively. The patients were investigated on an out-patient basis with their ordinary diet. All patients had hyperoxaluria. The oxalate excretion did not seem to decrease with time after operation. The patients operated with a biliointestinal shunt had a significantly higher excretion of oxalate than those with the other two types of operation, indicating that variations in the anatomy of the small intestine after jejunoileal bypass might result in different absorption of oxalate or oxalate precursors. Urinary oxalate, calcium oxalate saturation and ion-activity products were higher whereas the excretion of calcium, magnesium and citrate was lower in patients than in controls. The urine volumes, excretion of creatinine and urate and inhibition of calcium oxalate crystal growth were equal in patients and controls. Analogous urine composition was found in patients both with and without urolithiasis with the exception of a higher magnesium excretion observed in stone formers.

Adult↗
PubMed1983

Studies of liver insulin receptors in non-obese and obese human subjects.

The insulin-binding isotherms and the structural composition of human liver insulin receptors were examined by using plasma membranes that were prepared from liver biopsies of nine non-obese and 10 obese subjects undergoing elective surgery. The insulin-binding characteristics of liver membranes from non-obese subjects were quite similar to those previously described in rat liver membranes. However, when the membranes from obese subjects were compared with the non-obese group, insulin-binding activity was reduced by 50% (P less than 0.01). The reduction in obesity resulted primarily from a decrease in total receptor number, although a small decrease in receptor affinity was also observed. Insulin binding was not correlated with sex or with the fasting plasma insulin level. The insulin-binding sites of liver membranes were affinity-labeled with 125I-insulin and the cross-linking reagent, disuccinimidyl suberate. The liver membranes from both the non-obese and the obese group had heterogenous (nonreduced) insulin-binding species of 300,000, 260,000, and 150,000 mol wt, which were again comparable to the findings reported in rat liver. Sulfhydryl reduction demonstrated a major sub-unit of 125,000 and a minor component of 40,000-45,000 in both groups. These results indicate a close similarity between the hepatic insulin receptor of man and the more intensely studied rat hepatic receptor. Obesity in human subjects is associated with a loss of hepatic insulin receptors. This alteration may contribute to the insulin resistance reported in this organ as well as to obesity-mediated glucose tolerance.

Adult↗
PubMed1983

Low-oxalate, low-fat dietary regimen in hyperoxaluria following jejunoileal bypass.

Previous studies have shown that the severity of enteric hyperoxaluria can be reduced in hospitalized patients who receive a diet low in oxalate and fat. Little is known of the value of such a diet in the patients' home conditions. Ten patients with hyperoxaluria (greater than 0.45 mmol/24 h) following jejuno-ileal bypass were therefore studied while on their ordinary diet and also on a diet with low-oxalate, low-fat content. The mean urinary excretion of oxalate decreased during the dietary treatment from 1.1 to 0.7 mmol/24 h. The diet was demanding, though not unfeasible for the patients. Careful and regular dietary information, preferably by a dietitian, is recommended in such cases.

Adult↗
PubMed1983

Effects of calcium, aluminium, magnesium and cholestyramine on hyperoxaluria in patients with jejunoileal bypass.

The urinary excretion of oxalate, calcium, magnesium and citrate as well as the inhibition of calcium oxalate crystal growth in diluted urine was studied in seven patients with hyperoxaluria following jejunoileal bypass. The study was performed on an outpatient basis before and during daily administration of 38 or 113 mmol calcium, 28 mmol of aluminum, 20 mmol of magnesium or 16 g of cholestyramine. Each substance was administered for seven days with a free interval of at least seven days. The mean urinary oxalate excretion was not reduced with any of these regimens. Administration of 38 mmol of calcium per day resulted in increased oxalate and magnesium excretion. Increased excretion of both calcium and citrate was observed during administration of 113 mmol of calcium per day. Calcium and magnesium excretion was increased with aluminium. An increased magnesium excretion was also observed during administration of magnesium, resulting in a decreased calcium/ magnesium ratio. Cholestyramine resulted in increased oxalate and decreased citrate excretion.

Adult↗
PubMed1983

Manometric studies of lower esophageal sphincter in extreme obesity.

Esophageal manometry was performed in a group of extremely obese subjects in order to investigate the lower esophageal sphincter (LES) pressure and its relationship to extreme obesity, weight reduction and altered anatomy of the stomach. Forty subjects were examined before gastric surgery for treatment of their obesity, and 14 of these were reexamined after weight reduction. Normal LES pressure (20 mmHg) was found before operation, and also normal length and position of the LES. No significant changes were found in the group which was examined twice. In persons younger than 50, LES manometric findings do not seem to be influenced by extreme obesity, weight reduction or gastric surgery for obesity.

Body Weight↗
PubMed1982

Hydrophobic surface properties of myosin in solution as studied by partition in aqueous two-phase systems: effects of ionic strength, pH and temperature.

Affinity partitioning in dextran-polyethylene glycol-water biphasic systems has demonstrated that myosin has hydrophobic surface properties. In 0.5 M KCl at pH 7.5 myosin is transferred at increasing amounts to the polyethylene glycol-rich upper phase when an increasing proportion of that polymer in the system is replaced by its ester with lauric, myristic or palmitic acid. This shows that on its surface myosin has binding sites with affinity for long chain fatty acyl groups. Partition studies on the ionic strength range of 0.2-0.6 M KCl at pH 7.5 at 4 degrees C and 20 degrees C, respectively, in systems containing polyethylene glycol-palmitate showed that the affinity of myosin for the palmitate group becomes greater with (1) an increase in ionic strength, and (2) an increase in temperature at constant ionic strength. The affinity of myosin for the palmitate group also increases with a decrease in the pH in the range of 5.6-8.5. The increase in the affinity of myosin for the palmitate group parallels the increase in the tendency of myosin to self-interact and yield filaments.

Animals↗
PubMed1982

A roentgenological study of the small intestine after different intestinal bypass operations for treatment of morbid obesity.

Twenty-nine patients who had undergone four different types of jejunoileal bypass for obesity were examined roentgenologically after ingestion of barium contrast. Functional intestinal length, blind loop reflux and speed of contrast through the small intestine were recorded. Weight loss was not correlated to any of the mentioned parameters or to operative method. Length of functioning intestine increased and speed of contrast decreased with time after surgery.

Barium Sulfate↗
PubMed1982

Hepatic cholesterol metabolism in obesity: activity of microsomal 3-hydroxy-3-methylglutaryl coenzyme A reductase.

Obesity is often associated with an elevated total body cholesterol synthesis. In order to evaluate the role of hepatic cholesterogenesis in this phenomenon, we assayed the rate-limiting step in cholesterol biosynthesis, 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase in the microsomal fraction of liver biopsies obtained operatively from ten morbidly obese (relative body weight greater than 155%) subjects. Eighteen normal-weight patients (relative body weight less than 120%) with cholesterol gallstones served as controls. Hepatic HMG CoA reductase activity, expressed as pmol X min-1 X mg protein-1, was 60% higher in the obese subjects compared to the gallstone patients (P less than 0.05). Microsomal protein concentration was lower in the obese patients, so that enzyme activity calculated per gram liver was not significantly different between the two groups. However, mevalonate formation, expressed in terms of total organ activity, was higher in the obese than in the nonobese group. The results suggest that the liver is a major contributor to the increased cholesterol production seen in obesity.

Adult↗
PubMed1981

Effect of Cibachron Blue F3GA on the polymerization of actin.

The effect of the dye Cibachron Blue F3GA on the G-F transformation of rabbit muscle actin has been studied with viscosimetry. The presence of the dye which is known to bind to nucleotide binding sites, decreased both the initial rate of polymerization of actin as well as the final viscosity of actin. Both these effects can be ascribed to an increase in the critical concentration of actin. The inhibitory effect of Cibachron Blue F3GA was counteracted by ATP, suggesting a competition between Cibachron Blue F3GA and ATP for the binding site/sites on actin.

Actins↗
PubMed1981

Binding of human carbonic anhydrase to human hemoglobin.

The ability of human carbonic anhydrases to interact with human CO-hemoglobin have been studied with the counter-current distribution technique in aqueous/aqueous biphasic systems. The experimental results show that human carbonic anhydrase II interacts with human CO-hemoglobin whereas human carbonic anhydrase I does not. THe interaction between CO-hemoglobin and carbonic anhydrase II was quantified using the theoretical model developed previously for one-to-one interacting systems. [Backman, L. and Shanbhag, V.P. (1979) J. Chromatogr. 171, 1-13]. The apparent association constant was estimated to be 4.1 x 10(5) l mol-1 at pH 8.0 and 21 degrees C for the association of carbonic anhydrase II and CO-hemoglobin.

Carbonic Anhydrases↗
PubMed1981

Oxalate metabolism in man studied during total parenteral nutrition.

The mean urinary excretion of oxalate was 325 micromol/24 h in six patients during total parenteral nutrition (TPN). The urinary excretion of oxalate was considered to be equal to the endogenous oxalate production. A 2-day load of the oxalate precursor glycine given to five patients did not influence the oxalate excretion in spite of increased serum glycine concentrations. A 3-day load of the oxalate precursor ascorbic acid given to four patients increased the oxalate excretion in all patients. In one patient TPN was prolonged for 20 days without any change in the amount of oxalate excreted.

Adult↗
PubMed1981

Oxalate metabolism after intestinal bypass operations.

Hyperoxaluria and kidney stones are frequent following intestinal bypass operations. The urinary oxalate excretion was studied for 10-13 days during enteral and parenteral nutrition in six patients operated on because of massive obesity with a jejunoileostomy. The oxalate excretion in urine was higher than normal in all patients on normal diet. The excretion decreased on low-oxalate diet. Further decrease was observed during total parenteral nutrition (TPN). The oxalate excretion was stabilized at a low level within 48 h after the start of TPN and was unchanged during the rest of the study. This included a period of 2 days when a load of the oxalate precursor glycine (10 and 20 g) was given parenterally to five patients, resulting in increased serum glycine concentration. A slight decrease in oxalate excretion was found when the amino acid part (Vamin with 10% glucose) of the TPN solution was given enterally instead of parenterally in two patients. This study has indicated that the main reason for hyperoxaluria in patients with intestinal bypass operations is hyperabsorption of dietary oxalate. It seems likely that these patients have a normal endogenous oxalate production.

Adult↗
PubMed1980

Difference in kidney stone incidence after three types of intestinal bypass operations.

Jejuno-ileal bypass operations have been used for more than 20 years for the treatment of massive obesity. This treatment results in malabsorption with diarrhoea, especially during the first year after operation. A high incidence of urinary tract calculi was found in these patients (Backman & Hallberg, 1972; Dickstein & Frame, 1973; O'Leary, Thomas & Woodward, 1974; Backman et al., 1975; Gregory et al., 1975). Other known late complications are transient disturbances in liver function and electrolyte balance (Backman et al., 1975). Different types of operations result in different frequencies of kidney stones.

Adolescent↗
PubMed1980

Granulocyte-function in pancreatitis. Nitroblue tetrazolium-test related to clinical signs of bacterial infection and to hypertriglyceridemia.

Out of 26 patients with acute pancreatitis, 8 had several signs of bacterial infection such as high nitroblue tetrazolium (NBT) reduction of granulocytes, fever, elevated ESR and leukocytosis with granulocytosis. 2 patients had a high NBT-value without all other clinical signs of infection and 6 had such signs without a high NBT-value. --An NBT-value lower than normal was found in 6 patients, 3 of whom also had other signs of infection. The level of serum lipids, determined in only 3 of the 6, demonstrated concomitant hypertriglyceridemia. Hyperlipidemia is known to decrease granulocyte activity and might have prevented a stimulation to increased NBT-reduction otherwise brought about by bacterial infection. Further, 3 of the 6 patients with low NBT-reductions suffered from a very severe type of pancreatitis and two of them developed pneumonia. --Bacterial infection may thus contribute to a severe clinical course of pancreatitis, especially in patients with hypertriglyceridemia in whom the granulocyte function is depressed.

Acute Disease↗
PubMed1979

Role of hemoglobin in proton transfer to the active site of carbonic anhydrase.

The binding of bovine oxyhemoglobin to bovine carbonic anhydrase with a dissociation constant between 10(-5) and 10(-7) M has been determined by countercurrent distribution using aqueous, biphasic polymer systems. This result provides an explanation for the very efficient proton transfer between hemoglobin and carbonic anhydrase, a transfer which enhances the catalytic activity of carbonic anhydrase as measured by 18O exchange between bicarbonate and water at chemical equilibrium (Silverman, D. N., Tu, C. K., and Wynns, G. C. (1978) J. Biol. Chem, 253, 2563-2567). Two rate constants describing 18O exchange activity of carbonic anhydrase at pH 7.5 show saturation behavior when plotted against hemoglobin concentration consistent with a dissociation constant of 2.5 X 10(-6) M between bovine hemoglobin and carbonic anhydrase. Interpretation of these rate constants in terms of a two-step model for 18O exchange indicates that hemoglobin enhances the rate of exchange from carbonic anhydrase of water containing the oxygen abstracted from bicarbonate, but does not affect the catalytic interconversion of CO2 and HCO3- at chemical equilibrium.

Animals↗
PubMed1979

Protein-protein interactions studied by counter-current distribution. I. Theoretical computations.

Many biological macromolecules are known to interact either with themselves, with other macromolecules or with small compounds. A simple equilibrium method for detecting and quantifying these interactions is to study the mutual influence of the molecules on their respective counter-current distribution in liquid-liquid biphasic systems. The theoretical counter-current distribution patterns for the components in an interacting system, A + B in equilibrium AB, have been calculated for two models in order to establish the boundary conditions and to optimize the experimental procedure. The patterns have been calculated for a range of association constants, partition coefficients and initial concentrations of the two reactants.

Countercurrent Distribution↗
PubMed1979

The incidence of urinary tract calculi after small-intestinal bypass operations for treatment of obesity.

Jejunoileal bypass operations have been used for more than 20 years for the treatment of massive obesity. This treatment results in malabsorption with diarrhoea, especially during the first year after the operation. A high incidence of urinary tract calculi have been found in these patients (4, 5, 15, 19, 24). Other known late complications are transient disturbances in liver function and electrolyte balance (5).

Adolescent↗