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Biomedical subjects

L Backman

Publications and source records attributed to L Backman.

At least 91 records · Page 5Linked to original sources

Shape changes of the human red cell studied by aqueous two-phase partition.

Aqueous two-phase systems have been used to study the human red cell during metabolically induced shape changes. When the discoid character of the cells was lost in favour of echinocytic forms, the partition increased both in charge-sensitive and in charge-insensitive two-phase systems. Reversal of the shape transformation by ATP repletion not only led to shape recovery but also restored the initial partition. Therefore it is apparent that red cells exhibit a shape-dependent partition behaviour. As the partition is dependent on surface properties (such as charge and hydrophobicity) of the partitioned material, the results show that the shape changes caused rearrangement of the membrane and thereby exposure of or greater accessibility of binding groups on the cell surface. The similar partition behaviour in the charge-sensitive and charge-insensitive phase systems show that the increased partition was caused mainly by increased hydrophobic interactions between the cells and the upper phase. The observed partition behaviour therefore suggests that the echinocytic cells acquire a higher affinity for the upper phase by repacking the lipid bilayer or at least the outer leaflet into a less efficient packed and thus more fluid structure.

Erythrocytes↗

Complement activation and reinfusion of wound drainage blood.

Eighteen patients undergoing total hip replacement (n = 13) or knee arthroplasty (n = 5) due to osteoarthritis or osteoarthrosis were prospectively studied in an investigation of complement activation and anaphylatoxin release in association with reinfusion of aspirated wound blood. Twelve of the patients needed blood transfusions and received an average of 390 +/- 75 ml (+/- SD) of autologous blood within 45 min. Plasma complement components, anaphylatoxins, and inhibitors were studied 1 min before and 15 min after the start of and 15 min after the completion of autologous transfusion. Samples also were taken from the collected blood, before and after passing it through a microporous filter. Blood gases and systemic complement samples were drawn simultaneously. There were no significant changes in systemic complement variables before, during, or after transfusion of autologous blood. However, in the aspirated blood, increased concentration of anaphylatoxins (C3a and C5a) and terminal complement complexes (TCC) were present (P less than 0.001). There were no differences observed between samples drawn before and after filtration of the blood. The concentration of C5 was less in the collected blood than in the systemic blood (P less than 0.05). No changes in blood gases were observed. This study demonstrated that postoperatively salvaged whole blood underwent anaphylatoxin formation and complement activation. However, after reinfusion of this blood, neither systemic complement activation nor clinical complications were observed.

Adult↗

Omeprazole or high-dose ranitidine in the treatment of patients with reflux oesophagitis not responding to 'standard doses' of H2-receptor antagonists.

Ninety-eight patients (26 females), who presented with erosive and/or ulcerative oesophagitis, despite at least a 3-month period of treatment with standard doses of cimetidine (greater than or equal to 1200 mg daily) or ranitidine (greater than or equal to 300 mg daily), were included in a double-blind, randomized trial to compare omeprazole (40 mg o.m.) with a high dose of ranitidine (300 mg b.d.). The treatment was given for 4-12 weeks; endoscopy assessment and laboratory screening were performed on entry to the trial and thereafter every fourth week. Endoscopic healing was defined as complete epithelialization of all macroscopic erosions or ulcers in the squamous epithelium. An 'intention-to-treat' analysis of the clinical data revealed omeprazole to be superior to ranitidine: 63% of those patients who were given omeprazole were healed endoscopically after a 4-week period of treatment, compared with only 17% of those given ranitidine. This difference in healing rate persisted during the 12-week study period (90% vs 47% after 12 weeks; P less than 0.0001). Reflux symptoms were more rapidly and completely relieved with omeprazole: heartburn resolved completely in 86% of patients treated with omeprazole for 4 weeks compared with 32% in the ranitidine group (P less than 0.0001). The mean basal gastrin concentrations increased only in those given omeprazole from 18.9 pmol/L at pre-entry to a mean value of 31.7 pmol/L on the last day of omeprazole administration. In ranitidine-treated patients no significant increase in basal gastrin concentration was observed. Both drugs were well tolerated with few adverse events, which were mainly mild and transient. These results demonstrate the superiority of omeprazole over a high dose of ranitidine in the treatment of resistant reflux oesophagitis.

Adult↗

Fetal growth retardation after gastric banding.

A 35-year-old woman became pregnant 15 months after gastric banding, during which time she lost 55 kg in weight. During the third trimester, severe vomiting was noted and she lost a further 6 kg. Ultrasound examination showed oligohydramnions and fetal growth retardation of 38%. Enteral nutrition was given until delivery and ultrasound verified normalization of the oligohydramnions and weight gain for the fetus. The woman was delivered by cesarean section of a female infant with birthweight 2,470 g. It is concluded that special care must be taken with regard to the nutritional status of pregnant women who have previously been operated on with gastric procedures for obesity, in order to diminish the risk of fetal growth retardation. Ultrasound examinations should be performed on wide indications and enteral nutrition must start immediately once fetal growth retardation is discovered.

Adult↗

Apparent lack of effect of obesity on the soluble phosphatidic acid phosphatase activity in human adipose tissue.

In view of previous reports that the activity of the Mg(++)-dependent phosphatidic acid phosphatase in adipose tissues of rat and mouse is elevated in obesity, we attempted to assay this activity in biopsies of human omental adipose tissue obtained from normal-weight and morbidly obese subjects in connection with operations. The major portion of the phosphatidic acid phosphatase activity was found in the cytosol, and the small amount found in the microsomal fraction was too low for accurate measurement. It was not possible to assay the activity in the crude cytosol. After precipitation with ammonium sulfate, however, the enzyme activity was linear with both the incubation time and the concentration of enzyme. It was not possible to obtain substrate saturation of the enzyme under the conditions employed. When assayed in the presence of a high concentration of substrate (0.6 mmol/l) the activity obtained in normal-weight patients, 7.8 +/- 2.4 nmol/mg protein/min (n = 10), was not significantly different from that in morbidly obese patients, 5.6 +/- 0.8 nmol/mg protein/min (n = 10). There was no relation between the size of adipose cells and phosphatidic acid phosphatase activity. Furthermore, there was no apparent relation between phosphatidic acid phosphatase activity in omental adipose tissue and that in the liver. The findings suggest that the increased biosynthesis of triglycerides in human obesity is not associated with an increased capacity of the soluble phosphatidic acid phosphatase in adipose tissue.

Adipose Tissue↗

Polyneuropathy following gastric banding for obesity. Case report.

A 20-year-old woman was admitted to hospital with acute, severe neurologic symptoms 16 weeks after gastric banding for obesity. Her postoperative weight loss was 52 kg. Before admission she had protracted periods of vomiting with; hypokalemia. The etiology of the neurologic findings remains unclear. She responded slowly to adequate nutrition and recovered within 2 years.

Adult↗

Elevated plasma levels of oxytocin in obese subjects before and after gastric banding.

Impaired glucose tolerance and hyperinsulinaemia are common features of obesity. Since oxytocin has been shown to influence glucose metabolism and insulin secretion, the objective of the present study was to investigate whether the plasma level of oxytocin is elevated in obese subjects and if so, whether it is affected by weight reduction following gastric banding. Repeated blood samples were collected in connection with ingestion of a liquid test meal from subjects weighing about 130 kg. Normal weight subjects were tested likewise. Further tests were performed on obese subjects 6 months after operation with gastric banding and a subsequent weight reduction of about 30 kg. Plasma levels of oxytocin were measured by radioimmunoassay. It was found that plasma levels of oxytocin were 4-fold higher in the obese subjects when compared to the control subjects. Analysis with high performance liquid chromatography demonstrated that the oxytocin-like material, as determined by radioimmunoassay, in extracted plasma from one obese subject coeluted with synthetic oxytocin standard. Ingestion of a test meal did not seem to influence oxytocin levels. The mean oxytocin level was equally elevated in male and female obese subjects. Following operation oxytocin levels decreased significantly, but were still significantly higher than in the control subjects. The mechanism behind the hyperoxytocinaemia and possible consequence of it remain obscure.

Female↗

Influence of calmodulin on the human red cell membrane skeleton.

The calcium receptor calmodulin interacts with components of the human red cell membrane skeleton as well as with the membrane. Under physiological salt conditions, calmodulin has a calcium-dependent affinity for spectrin, one of the major components of the membrane skeleton. It is apparent from our results that calmodulin inhibits the ability of erythrocyte spectrin (when preincubated with filamentous actin) to create nucleation centers and thereby to seed actin polymerization. The gelation of filamentous actin induced by spectrin tetramers is also inhibited by calmodulin. The inhibition is calcium dependent and decreases with increasing pH, similar to the binding of calmodulin to spectrin. Direct binding studies using aqueous two-phase partition indicate that calmodulin interferes with the binding of actin to spectrin. Even in the presence of protein 4.1, which is believed to stabilize the ternary complex, calmodulin has an inhibitory effect. Since calmodulin also inhibits the corresponding activities of brain spectrin (fodrin), it appears likely that calmodulin may modulate the organization of cytoskeletons containing actin and spectrin or spectrin analogues.

Actins↗

Serum gastrin, insulin and somatostatin levels in normal and obese subjects before and after gastric banding.

The postprandial secretion of insulin, gastrin and somatostatin was studied in 23 extremely obese subjects and nine normal-weight controls after a liquid test meal. Apart from a significantly higher insulin level in the obese group, no significant intergroup difference was found. The effect of weight loss on the same hormones was studied in 18 patients 6 months after gastric banding. The mean weight loss during this period was 33 +/- 2.1 (SEM) kg. There was significant decrease in postprandial insulin secretion after gastric banding, but neither gastrin nor somatostatin levels were altered.

Adult↗

Technical complications and related reoperations after gastric banding.

Seventy-two patients who underwent gastric banding for extreme obesity were followed for a mean of 30 (range 12-54) months. The mean weight loss after 1 year was 41 kg. About two-thirds of the patients had only minor complaints postoperatively, but the others had complications, some of which were serious. Two patients died. Complications related to the banding technique necessitated 33 reoperations in 22 patients. The most common cause of reoperation/complication was functional stenosis of the upper pouch outlet, but only 3 of 22 revisional operations were successful. Reduction in band tension resulted in fewer reoperations but also less weight loss. The incidence of complications and the poor outcome of revision indicate that gastric banding should still be regarded as an experimental operation. Peroperative measurement of all technical details and careful and frequent follow-up examination are necessary in the search for an optimal technical procedure, giving good weight loss with a minimum of complications.

Adult↗

Gastric acid secretion in extremely obese subjects before and after gastric banding.

The gastric acid secretion was studied in 17 extremely obese patients after injection of synthetic gastrin (Peptavlon). The mean basal acid output (BAO) and the peak acid output (PAO) were both within normal range. Positive correlation was found between PAO and body weight. Gastric banding was performed as treatment of the obesity, and the gastric acid secretion was studied in the proximal and the distal pouch after a mean postoperative interval of 8 (range 4-20) weeks. BAO was similar after banding, but PAO was significantly decreased (from 26.3 +/- 3.6 to 16.2 +/- 2.2 mmol/h). PAO and BAO were almost identical in the two pouches, despite great difference in their size.

Adult↗

Comparison between subjective and objective estimates of upper pouch volume at gastric banding for obesity.

Small size of the upper pouch has been considered mandatory for good weight loss after different gastric operations for extreme obesity. In most published series the estimates of upper pouch size seem to have been subjective. The present report concerns gastric banding in 18 patients, with standardized objective measurement of the upper pouch made after subjective estimation independently by two bariatrically trained surgeons. The subjective determination resulted in statistically significant underestimation compared with the objective procedure. For adequate evaluation of the surgical method, therefore, it is important to measure the pouch size objectively.

Adult↗

Weight loss and some metabolic consequences of gastric banding with different band tension.

The results of gastric banding for obesity were studied in 72 patients. The tension of the band around the stomach was successively decreased because of vomiting. The change resulted in less problems with vomiting and fewer reoperations, but also less weight loss. Statistically significant correlation was found between the Broca index before gastric banding and a year later. The superobese patients (greater than 100% overweight) had significant residual obesity when they reached stable body weight after about a year. Some metabolic changes were found postoperatively, e.g. improved results of liver function tests, reduced serum triglycerides, commonly sideropenia and occasionally hypokalemia.

Adult↗

The 240-kDa subunit of human erythrocyte spectrin binds calmodulin at micromolar calcium concentrations.

The binding of the isolated alpha-subunit of human erythrocyte spectrin to calmodulin is demonstrated by partitioning in aqueous two-phase systems. The affinity of the alpha-subunit for calmodulin is slightly higher than that of the spectrin dimer, whereas the beta-subunit interacts only very weakly. The binding is in all cases calcium-dependent and is abolished on addition of chlorpromazine. At an ionic strength close to physiological conditions, about 1 microM free calcium is required to induce maximum binding of calmodulin to spectrin dimer.

Calcium↗

Tissue reaction to polypropylene and polyester in obese patients.

Local tissue reaction was examined after subcutaneous implantation for 8 wk of small pieces of Marlex (polypropylene) and Dacron (polyester) in 11 extremely obese patients. Dacron gave a stronger chronic inflammatory reaction in 7 out of 11 patients, and a stronger foreign body giant cell reaction in all of them: Marlex is therefore perhaps more suitable than Dacron as a reinforcement band in gastric surgery for obesity. At reoperations due to complications after gastric banding the tissue reaction in the omentum which covered the band, was examined in 9 patients. No major difference in tissue reaction in the omentum compared to that in subcutaneous fat was found. None of the reoperations was caused by too strong a tissue reaction to the reinforcement band i.e. Marlex in 8 patients and Gore-tex (Teflon) in one patient.

Biocompatible Materials↗