Behavior of F-response and determination of actively involved motoneurons

Fifteen nerves were examined in 10 healthy subjects, using a collision technique with 2 stimulation pulses of different intensity on the same point. The F-waves which occurred after the antidromic activation of the motor neuron cells by the first supramaximal pulse were blocked on their return pathway by the collision with the depolarization induced by the second pulse. The progressive decrement of the voltage of the second stimulus allowed, the transmission of the recurrent discharge along motor fibers with a lower depolarization threshold. The amplitude and the persistence of the F-waves increased (p < 0.05 and p < 0.001 respectively), while their latency decreased (p < 0.01) concurrent with the liberation of additional motor neurons with a lower threshold of depolarization. These findings suggest that the F-wave may be elicited in motoneuron of different depolarization threshold but primarily in larger and faster nerve fibers, with a lower threshold of depolarization.

Withdrawal of the aldose reductase inhibitor tolrestat in patients with diabetic neuropathy: effect on nerve function. The Tolrestat Study Group

A double-blind, placebo-controlled clinical trial was conducted to study the effects of discontinuing tolrestat, an aldose reductase inhibitor, on peripheral sensorimotor diabetic neuropathy. After an average of 4.2 years of continuous tolrestat use, 372 patients were randomly assigned to either placebo or continued tolrestat therapy and were followed for 52 weeks. After 3 months, patients who perceived worsening of symptoms of neuropathy were allowed to switch once to the alternate treatment group while maintaining the double-blind. Patients assigned to placebo had significant deterioration in motor nerve conduction velocity (MNCV) while those maintained on tolrestat did not (p < 0.05). The 28 patients who were randomly assigned to tolrestat and elected to switch to placebo had a significant deterioration in MNCV while the 36 assigned to placebo who switched to tolrestat had a significant improvement (p < 0.05). Treatment differences in favor of tolrestat were observed for sensation in the toes as well as for pain (p < 0.05). These data indicate that withdrawal from long-term treatment with tolrestat has a detrimental effect on several measures of diabetic neuropathy, whereas continuation of treatment is associated with stabilization of these measures, suggesting a continued role for polyol pathway activity in late neuropathy.

Effect of hyperglycemia and the aldose reductase inhibitor tolrestat on sural nerve biochemistry and morphometry in advanced diabetic peripheral polyneuropathy. The Tolrestat Study Group

Tolrestat is a well tolerated nonhydantoin aldose reductase inhibitor that has been reported to improve nerve conduction in diabetic animals and humans. Its effects on nerve biochemistry and structure have not been studied in patients with diabetic neuropathy. Patients with advanced diabetic neuropathy treated with long-term open-label tolrestat were randomly assigned to continuation on drug treatment or to placebo-controlled drug withdrawal for 12 months. At the end of this period, sural nerve biopsies were obtained for measurement of glucose, sorbitol, and fructose content, and for detailed morphometric analysis. Tolrestat ameliorated the glucose-mediated increase in sorbitol and fructose in sural nerve tissue. No statistically significant differences in nerve morphometry emerged between the two groups; however, both treatment groups exhibited increased nerve-fiber regeneration and normalization of axo-glial dysfunction and segmental demyelination following long-term tolrestat treatment. These findings are similar to those previously reported in a placebo-controlled sequential nerve biopsy study with the aldose reductase inhibitor sorbinil. Thus tolrestat is a biochemically effective aldose reductase inhibitor in human diabetic nerve with potential therapeutic efficacy for diabetic neuropathy.

Possibilities of interference with the immune system of tumor bearers by non-lymphoid Fc gamma RII expressing tumor cells

The ectopic expression of Fc gamma RII by PyV transformed 3T3 cells derived from tumors of long latency has been established. It was suggested that this expression is one of several changes conferring upon the cells an increased capacity for survival. We found that in one case cells expressing a very high level of Fc gamma RII had also a very high metastatic phenotype as compared to FcR negative cells. Direct evidence that Fc gamma RIIbl functions as a progression factor was provided by transfection experiments. The transfected gene conferred an increased malignancy and invasive phenotype upon PyV or c-Ha-ras transformed cells. In the present study we tested the possibility that Fc gamma RII expressing tumor cells could interfere with the immune system. The following subjects were investigated: 1) The ability of Fc gamma R on the tumor cells to bind the ligand and/or release IBF. 2) The effect of a local accumulation of ligand and/or IBF (assumed to take place in situ in the tumor) on Fc gamma RII expressing T cells. It was found that both tumor-derived receptor positive and beta l transfected PyV transformed cells were capable of binding aggregated mouse IgG. The binding of bivalent ligand was followed by an increase in membrane Fc gamma RII expression. Also both types of cells were capable of releasing IBF. We then tested the possibility that a local accumulation of IgG within the tumor could effect Fc gamma R expressing T cells. It was found that aggregated mouse IgG (as well as IgGl) could stimulate the proliferation of the T cell hybridoma (T2D4) and other Fc gamma RII expressing T cells. We also found that the expression of beta Fc gamma RII specific mRNA peaked at the logarithmic phase of T2D4 cultures, in parallel with their maximal potential to release IBF. Several pathways for interference with the immune system are suggested.

Phenotypic properties of 3T3 cells transformed in vitro with polyoma virus and passaged once in syngeneic animals

Cloned BALB/c 3T3 cells transformed in vitro with polyoma virus (PyV) acquired a higher tumorigenicity phenotype after a single in vivo passage. Some of the in vivo passaged cells (CTC cells) exhibited also a higher metastatic phenotype than cells from the same clones that were maintained only in culture (C cells). A phenotypic comparison between CTC and C cells was performed. It was found that most CTC lines exhibited a higher binding to laminin compared to their clonal C cell ancestors. Some CTC cells were less sensitive to the cytotoxic effects of TNF-alpha than the corresponding C cells. CTC cells originating from tumors which appeared after a long latency period (late tumors) tended to express Fc gamma RII while CTC cells originating from tumors which appeared after a short latency period (early tumors) as well as the corresponding C cells tended not to express Fc gamma RII. The expression of a membrane epitope recognized by a monoclonal antibody expressing specificity towards PyV transformed cells, was down-regulated on late tumor cells compared to early tumor cells. Transfection of cloned PyV-transformed BALB/c 3T3 cells with the beta 1Fc gamma RII gene augmented the tumorigenicity and metastatic phenotype of the transfectants compared to control transfectants.

Diagnostic value of computer analysis of multipeaked EMG spikes

Computer analysis of absolute number of peaks per second and the number of peaks in the multipeaked spikes/sec was carried out in the EMG interference recordings of 5 healthy, 6 myopathic and 8 neuropathic subjects. The purpose of the study was to detect diagnostically different patterns. A spike was considered multipeaked if it had 6 or more peaks. The amplitude of elimination (baseline) was examined at 1: 5, 1: 10 and 1: 15 of the average amplitude per second. Both the number of peaks and the number of peaks in multipeaked spikes in the neuropathic and myopathic muscles showed statistically significant differences when compared to healthy muscles. This technique could give an indication for the differential diagnosis of myopathic, neuropathic or healthy state of the muscle.

In vivo tumorigenicity and in vitro sensitivity to tumor-necrosis-factor alpha mediated killing of c-Ha-ras-transformed cells

Cellular subclones of high and low tumorigenicity obtained from a mouse c-Ha-ras-transformed clone, were examined for their sensitivity to tumor-necrosis-factor (TNF)-mediated cytotoxicity. Cells of the highly tumorigenic subclones showed a significantly enhanced resistance to the cytotoxic effect of TNF plus cyclohexamide (CHI) as compared to cells of the low-tumorigenic subclones. The enhanced resistance to TNF+CHI was not due to a lower expression of TNF receptors on the cells. The c-Ha-ras-transfected cells were transformed and maintained in culture only (C cells). In vivo passage of cells of the initially low-tumorigenic c-Ha-ras subclones through the mouse significantly enhanced the tumorigenic potential of these CTC cells (culture/tumor/culture). In correlation with their enhanced tumorigenicity, the CTC cells were highly resistant to TNF-mediated cytotoxicity as compared to C cells of the same subclone. Furthermore, the involvement of TNF in determining the tumorigenic phenotype of the c-Ha-ras-transformed cells was demonstrated in a more direct manner. Cells of a c-Ha-ras-transformed low-tumorigenic, highly TNF-sensitive subclone were selected by repeated cycles of in vitro exposure to TNF alpha. As a result, a stable, highly TNF-resistant population of cells emerged. These TNF-resistant cells caused more tumors in mice as compared to their original TNF-sensitive cells. These results show that the resistance to the cytotoxic effect of TNF plus cyclohexamide may be involved, at least partially, in the tumorigenic potential of c-Ha-ras-transformed cells and suggest a possible role for TNF in the enhancement of the tumorigenic potential of these cells in mice.

Fourier series analysis of the electrophysiological pattern of fatigue in healthy human beings, after curare administration

Real time computer analysis of the electrophysiological development of muscular fatigue after small doses of d-tubocurarine (TC), has been examined in anesthetized human beings. As compared to a decrease of frequency in the control measurements, previous studies have shown an increase of the frequency of spikes after TC administration. The present experiments were carried out on the biceps brachii of 8 healthy human volunteers maintained in isometric contraction against a constant counter load until complete fatigue occurred. The Fourier spectrum analysis showed a statistically significant shift to lower frequencies before, and a milder statistically non significant shift after TC. These results may indicate that under mild curarization the early phase of muscular contraction requires a higher number of large motor units and thus, at a later stage of the contraction the pool of available large motor units becomes smaller. This conclusion supports the hypothesis that mild curarization causes a state of initial muscular fatigue.

Manometry and electromyography of the pharyngeal muscles in patients with dysphagia

Simultaneous recording of the electromyographic activity of the pharyngeal muscles and the intraluminal pressure in the upper sphincter zone was performed routinely in patients with swallowing problems for the first time, to our knowledge. This technique was found to be very useful for the localization of the "site of lesion." The procedure is safe, easy to master, and causes minimal inconvenience. It can reveal, in the most direct way, whether the disturbance is in the hypopharyngeal musculature (represented by the inferior constrictor muscle), in the cricopharyngeal muscle (spasm or lack of relaxation), or in the synchronization between them. Simultaneous recording of intraluminal pressure adds valuable information about the mechanical events associated with electromyographic activity. It was found that in pathologic cases there is quite often no correlation between the electrical and mechanical events. Thus, simultaneous recording of both electrical and mechanical events is essential for the understanding of the pathophysiology of disturbances of deglutition.

Electromyography of the inferior constrictor and cricopharyngeal muscles during swallowing

Electromyography (EMG) of the inferior pharyngeal constrictor (IC) and the cricopharyngeal (CP) muscle was recorded in 18 patients with swallowing and/or aspiration problems who were candidates for cricopharyngeal myotomy. The EMG recordings were compared to those of 13 "normal" subjects who did not suffer from such problems. Differences in EMG activity between the control group and the patient group were considered with respect to the clinical symptoms in the patient group. Recording of EMG in the CP and IC muscles is relatively safe, useful, and easily mastered. The technique may provide important information regarding the function of some of the muscles involved in deglutition.

Comparison of the electrophysiological pattern of fatigue between athletes required to perform explosive and endurance sports

The electrophysiological behavior of an isometric contraction sustained to fatigue, was examined in 6 long distance runners and 9 athletes involved in explosive (burst) sports, by on line computer analysis of the electrical activity of vastus medialis, rectus femoris and vastus lateralis. The experiments were carried out with a counterload of 50% of the maximal strength of the muscle. The duration of spike increased and the frequency decreased in the 3 examined muscles, in both types of sport. In the burst sports the changes of value of both parameters were statistically significant in the 3 muscles. In endurance sports the variations of duration were not significant and the changes of frequency were statistically significant only in the vastus lateralis. These results could be explained by the gradual activation of motor units of more strikingly different sizes in burst sports. Thus it may be speculated that prolonged training in burst sports may result in the automatic mobilization of higher number of small motor units, for the initiation of contraction while in endurance sports the onset of contraction is more gradual and carried out by large motor units.

Effect of filter setting on the electromyographic parameters of muscles contracting to fatigue

The effects of various filter settings on the electrophysiological behavior of the development of muscular fatigue were studied. Eleven healthy volunteers were examined during isometric contraction of biceps brachii and rectus femoris against a constant load until fatigue occurred. The electrical activity was taped and computer processing was carried out at the basic setting of 15-5000 cycles and at low (15-200 Hz) and high (200-5000 Hz) frequence filter. The results support the hypothesis that in the low range of frequencies there is a high density of large slow motor units, while in the high range of frequencies there are numerous small fast motor units.

Low density lipoprotein (LDL) inhibits histamine release from human mast cells

We examined the effect of low density lipoprotein (LDL) on histamine release from purified human lung mast cells. LDL inhibited anti-IgE- induced histamine release in a dose-dependent manner, with 100 micrograms/ml LDL-protein inhibiting histamine release by 53 +/- 8% (mean +/- SEM); half-maximal inhibition occurred at 40-80 micrograms/ml. LDL also inhibited calcium ionophore A23187-induced histamine release in a dose-dependent manner, with 1 mg/ml of LDL inhibiting histamine release by 83 +/- 9%; half maximal inhibition occurred at 220-280 micrograms/ml. Inhibition by LDL was time-dependent: half-maximal inhibition of anti-IgE- induced histamine release by LDL occurred at 30-50 minutes of incubation. The inhibitory effect of LDL was independent of buffer calcium concentrations (0-5 mM) or temperature (0-37 degrees C). These data are consistent with a newly defined immunoregulatory role for LDL.

Immunogenicity of malondialdehyde-modified low density lipoproteins. Studies with monoclonal antibodies

Malondialdehyde (MDA)-modified low density lipoprotein (LDL) can stimulate the accumulation of cholesteryl esters in cultured macrophages through its interaction with specific scavenger receptors. It has been speculated that such interaction occurs in vivo thus contributing to the formation of foam cells within atherosclerotic lesions. This report describes the development of new tools in the form of a specific assay for MDA-LDL to investigate this hypothesis. We have immunized BALB/c mice with malondialdehyde mouse low density lipoproteins and antibodies against malondialdehyde human low density lipoproteins were generated. Monoclonal antibodies were produced using hybridoma techniques and one particular clone (EB 7-3) was expanded for further studies. The immunoreactivity of several antigens was tested using antibody EB 7-3 in an enzyme-linked immunosorbent assay (ELISA). In a typical assay malondialdehyde human LDL (with at least 40% of lysines modified) was coated (2 micrograms/ml, 100 microliter) in 96-well microtiter plates. Antibody plus one of several antigens were then added and the interaction between the antibody and coated antigen was measured using alkaline phosphatase-conjugated affinity purified goat anti-mouse immunoglobulin. The binding of antibody EB 7-3 to wells coated with malondialdehyde-LDL was competitively inhibited by malondialdehyde-LDL added in solution, with half maximal inhibition occurring at 150 +/- 80 ng/ml. In addition, the ability of malondialdehyde-LDL to inhibit this interaction was proportional to the degree of modification: the more lysines were modified the more did malondialdehyde-LDL inhibit the binding of antibody EB 7-3 to coated malondialdehyde-LDL.(ABSTRACT TRUNCATED AT 250 WORDS)

Enzyme linked immunosorbent assay for the measurement of nonenzymatically glucosylated proteins in serum and in tissues

We have developed an enzyme linked immunosorbent assay (ELISA) for glucosylated proteins. The polyclonal antiserum was prepared against reduced glucosylated lipoproteins and was specific for the glucose-lysine bond. The antiserum recognized, in a dose-dependent manner, all reduced glucosylated proteins tested, including albumin, fibrinogen, low density lipoprotein, high density lipoprotein and hemoglobin, yet had no affinity for native proteins or to glucosylated but nonreduced proteins. The sensitivity of the assay was in the order of 1-5 pmol glucosylated lysine/ml and half maximal displacement occurred at 8-24 pmol glucosylated lysine/ml. The inter- and intraassay variables were 10.8% and 13.5%, respectively. Serum proteins from diabetic patients (n = 30) contained 84 +/- 6 picomoles of glucosylated lysine/mg protein, compared to 28 +/- 3 in controls (n = 20), and the concentration of glycosylated proteins correlated with fasting blood glucose (r = 0.56, p less than 0.02), but not with glucosylated hemoglobin levels (r = 0.29, p greater than 0.1). Proteins from diabetic glomeruli and aortae similarly contained more glucosylated lysine residues than controls.

Very low density lipoproteins (VLDL) trigger the release of histamine from human basophils

Circulating basophils are well established sources of the granule-associated mediator, histamine. The physiological control, however, of histamine release from human basophils is poorly understood. Because histamine may play a role in the transendothelial transport of various compounds, including very low density lipoprotein (VLDL) and its hydrolysis products, we investigated the possibility that VLDL regulates mediator release from basophils. The incubation of VLDL (at physiological concentrations) with basophils (isolated as mixed leukocyte preparations) resulted in a significant release of histamine. Histamine release was dependent on VLDL concentration (half-maximal stimulation occurring at VLDL-protein concentration of 15-20 micrograms/ml), length of incubation (half-maximal release at 5-12 min), temperature (37 degrees C optimum) and required calcium (concentration 0.5-2.0 mM). Furthermore, VLDL-induced histamine release was inhibited by three different mediator-release inhibitors: dimaprit, dibutyryl cAMP and nordihydroguaiaretic acid. Incubation of basophils with LDL or HDL under the same experimental conditions did not result in significant histamine release from basophils. The histamine-secretory response of basophils obtained from different donors varied considerably. Basophils isolated from 28 donors and challenged with 100 micrograms/ml VLDL released 23 +/- 5% of their cellular histamine (mean +/- S.E.; with a range of 0-94%). Desensitization of VLDL-induced histamine release could be accomplished by preincubation of basophils with either VLDL or anti-IgE but not with N-formyl-L-methionyl-L-leucyl-L-phenylalanine. Through the secretion of histamine, a potent vasoactive mediator (and also possibly through granule-associated glycosaminoglycans, stimulants of the enzyme lipoprotein lipase), this novel effect of VLDL may be part of a physiological loop for the regulation of VLDL hydrolysis and lipid transport. This effect of VLDL may also have deleterious consequences, because of the atherogenic properties of histamine.

Plasma levels of apoprotein B in patients with diabetes mellitus: the effect of glycemic control

Patients with diabetes mellitus often exhibit abnormalities in plasma lipoprotein concentrations. We have examined the effect of glycemic control (as assessed by hemoglobin A1 levels) on the concentrations of plasma lipoproteins and apoproteins in 109 patients with type I diabetes mellitus. HbA1 levels showed positive correlations with plasma LDL-cholesterol levels (r = 0.31; P less than 0.002) and triglyceride levels (r = 0.41; P less than 0.002), but not with HDL-cholesterol levels. The strongest correlation was between HbA1 and plasma levels of apoprotein B (r = 0.57; P less than 0.001). We have also examined the effect of long-term improvement in glycemic control (achieved with insulin infusion pump therapy) on plasma lipoproteins in six patients with type I diabetes. Patients were followed for 5 to 12 months, with mean (+/- SD) HbA1c levels decreasing from 11.4 +/- 2.5 to 9.1 +/- 1.8. Most, but not all, patients showed reduction in plasma LDL-cholesterol levels and increase in plasma HDL-cholesterol levels, but these did not reach statistical significance. Only the decrease in plasma apo B levels was statistically significant (from 112 +/- 38 mg/dL before pump therapy to 91 +/- 33 mg/dL at the end of the follow-up, P less than 0.05). We conclude that glycemic control plays an important role in regulating the levels of plasma LDL-cholesterol and triglycerides in patients with type I diabetes. Apoprotein B is a particularly sensitive indicator to alterations in glycemic control. It is possible that tight glycemic control may have "antiatherogenic" effects through reduction of apo B levels.

Altered HDL subclasses in endogenous hypertriglyceridemia are not affected by weight reduction

Reduction of body weight is commonly used to decrease the plasma lipids of patients with primary endogenous hypertriglyceridemia, but the effects of stabilized weight reduction on lipoprotein compositions and distribution are not well known. Since lipoprotein structures are perhaps as important in normal and abnormal metabolism and atherogenesis as are the levels of lipoproteins, we examined the effects of weight loss on the plasma concentrations, compositions, and ultracentrifugal flotation properties of plasma lipoproteins. Nine patients (eight males, one female) with endogenous hypertriglyceridemia and low high-density lipoprotein (HDL)-cholesterol levels who were approximately 130% of ideal body weight were studied during two dietary periods (basal and low weight). Subjects consumed an isocaloric diet for 5 weeks consisting of approximately 15% protein, approximately 45% carbohydrate, approximately 40% fat, approximately 500 mg/d cholesterol, P/S ratio 0.43 (basal), followed by a hypocaloric diet of the same composition, which was eaten for 16 to 52 weeks, until the desired weight was lost (9.6 +/- 3.6 kg). Then patients continued to eat a diet of the same composition lower in calories but sufficient in quantity to maintain their new lower body weights for the final 5 weeks (low-weight period). The last weeks of the basal and the low-weight periods were spent in a metabolic ward. Thus, high and low body weights were known to be stable for at least 5 weeks. Fasting (12 to 14 hours) plasma total triglycerides decreased in all patients (from 328 +/- 204 mg/dL at basal to 185 +/- 77 mg/dL at low weight, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Microrheologic investigation of erythrocyte deformability in diabetes mellitus

This study was undertaken to determine whether diabetes alters the viscoelastic properties of erythrocytes. The oldest and youngest 10% fractions of circulating red cells were separated by centrifugation of freshly drawn blood obtained from ten diabetics with disease of one to 20 years' duration and from an equal number of age- and sex-matched control subjects. Cells from each fraction were suspended in phosphate-buffered saline, and their rheologic behavior was examined in a rheoscope. The elongation of cells, the percentage of cells that tank-treaded in response to shear stress, tank-treading frequency, and the rate of recovery of cell shape upon cessation of shear stress were determined in the oldest and youngest 10% of cells for diabetics as well as for controls. All four parameters were virtually identical for diabetics and controls. Additional aliquots of cells were taken for assessment of nonenzymatic glucosylation of hemoglobin and cell membrane protein. The absence of any measurable difference in rheologic behavior of cells from diabetic and control subjects, despite substantial differences in nonenzymatic glucosylation of hemoglobin and cell membrane proteins, suggests that the magnitude of glucosylation observed in these cellular constituents does not alter the viscoelastic properties of the cells. The implication of these observations is that microvascular complications of diabetes are not attributable to altered deformability of red cells.

Age-related changes in deformability of human erythrocytes

The present study was designed to further the characterization of age-related changes in the deformability of human erythrocytes. The top (approximately young) and bottom (approximately old) 10% fractions of density-separated red cells from ten normal donors were subjected to graded levels of shear stress in a rheoscope. Measurements were made of steady-state elongation (cells tank treading in a state of dynamic equilibrium) and the time course of shape recovery following abrupt cessation of shear. In parallel with the rheologic experiments, several physical and chemical properties were assayed to determine correlates of mechanical properties. These included mean cell volume, mean corpuscular hemoglobin concentration, type A1 hemoglobin, glucosylation of membrane proteins, and membrane phospholipid and protein concentration. The microrheologic observations revealed that only about 90% of the old cells retained their capacity to tank tread. However, the tank-treading cells elongated less than their younger counterparts at corresponding levels of shear stress, thus demonstrating a reduced level of deformability. Further analysis of the data indicates that increases in membrane viscosity and elastic modulus along with a significant loss in excess surface area contribute to the limitation of the ability of the older cells to change shape.

Abnormal cell-interactive properties of low-density lipoproteins isolated from patients with chronic renal failure

Patients with renal failure on maintenance hemodialysis have accelerated rate of atherosclerosis. This, and the fact that chemically modified low-density lipoproteins (LDL) have a better capacity than native LDL to stimulate cholesteryl ester accumulation within macrophages in the vessel wall, led us to examine the possibility that some alteration in apo-LDL may take place in chronically uremic patients. We isolated LDL (d = 1.019 - 1.063 g/mL) from 18 patients with chronic renal failure and from 13 normolipidemic controls and compared the interactive properties of the different LDL preparations with cultured fibroblasts. Our results show that "uremic" LDL associates less, is degraded less, and has diminished ability to stimulate cholesteryl ester formation in fibroblasts when compared to normal LDL. LDL carbamylated in vitro showed interactive properties with fibroblasts similar to those of uremic LDL. Uremic LDL was not taken up by scavenger receptors present on rat peritoneal macrophages, similarly to normal LDL. However, the decrease in uptake by fibroblasts of uremic LDL may increase the residence time of these particles within the subendothelial region of the vessel wall, ultimately resulting in increased atherogenicity. Carbamylation of lysine residues of apoB in vivo, abnormal catabolism of LDL due to the absence of functional renal tissue, or triglyceride enrichment of LDL are among the possible explanations for the abnormal properties of uremic LDL.

Effect of exercise of the lower limbs on the non-exercised biceps brachii muscle

The electrophysiological pattern of fatigue of the biceps brachii (BB) muscle before and after bicycle leg exercise (LE), was evaluated in 12 healthy volunteers. In healthy people, the onset of isometric contraction is initiated by smaller motor units with briefer durations and higher spike frequencies. With the progression of contraction and muscular fatigue, electromyographic decrease in frequency and an increased spike duration occur. In our study, these findings were presented in subjects at the Final Value (FV) of electromyography before and after LE. In 8 subjects, the Initial Value (IV) of spike duration was longer after LE and a decrease in the frequency of electromyography was found in 9 of the 12 subjects. The changes in these two parameters at the onset of the BB contraction after LE may be due to the existence of an electrophysiological transfer effect. Eight subjects sustained the isometric BB contraction longer after LE than before LE. This may be explained by a diverting activity or other factors. Venous lactic acid was measured in 7 subjects and showed an increase after LE. No definite correlation between electromyographic changes and lactic acid was found.

The interaction of carbamylated low-density lipoprotein with cultured cells. Studies with human fibroblasts, rat peritoneal macrophages and human monocyte-derived macrophages

We determined the effects of various degrees of chemical modification of low-density lipoprotein (LDL) on its interaction with receptors present on human fibroblasts, human monocyte-derived macrophages and rat peritoneal macrophages. We isolated LDL (d = 1.019-1.063 g/ml) and carbamylated different numbers of lysine residues and tested its cell-interactive properties, including binding, degradation, and stimulation of [3H]oleate incorporation into cholesteryl oleate. Small carbamylation of LDL (approximately 1-2% of lysine residues) resulted in a reduced ability (70-80% of control) to displace 125I-labeled LDL from fibroblast receptors. Modification of 12.5-25% of lysine residues resulted in a marked increase in the ability of LDL to interact with scavenger receptors and an almost total loss in the ability to interact with apolipoprotein B-E receptors. Acetylated LDL and malondialdehyde-modified LDL inhibited competitively the degradation of 125I-carbamylated LDL by human macrophages. Thus, the extent of modification plays an important role in recognition of modified LDL by scavenger receptors. There also seems to be a range of modification over which LDL is not yet recognized by the scavenger receptor, but its interaction with the apolipoprotein B-E receptor is markedly reduced. This perhaps explains how a small in vivo modification of LDL can result in an increase in residence time of LDL in the subendothelial tissue which can lead to further local interactions, ultimately increasing the atherogenicity of the LDL particle.

Effect of probucol on the composition of lipoproteins and on VLDL apoprotein B turnover

We studied the effect of probucol on lipoprotein composition and VLDL apo B turnover. In 7 hypercholesterolemic subjects, probucol therapy lowered mean total cholesterol, HDL cholesterol and HDL triglycerides, raised LDL triglycerides and did not change LDL cholesterol. LDL cholesterol:LDL triglycerides mass ratios fell. In all 6 subjects studied by rate-zonal ultracentrifugation, the flotation rate of LDL decreased. The isolated LDL were depleted of cholesteryl esters relative to protein. Thus, there were changes in the physical and chemical properties of LDL. All 6 subjects had reductions in HDL2, with variable changes in HDL3 on zonal ultracentrifugation. Probucol did not cause significant alterations in VLDL apo B turnover in 4 patients. The results suggest that the alterations in HDL probably are not related to changes in the flux of VLDL plasma, but rather may be due to direct effects of the drug on HDL production or catabolism.

Increases in dietary cholesterol and fat raise levels of apoprotein E-containing lipoproteins in the plasma of man

Previous studies from this laboratory have determined that diets containing the usual amounts of fat to which are added 750-1500 mg/day cholesterol elevate the plasma cholesterol concentration by variable amounts, depending upon the ratio of polyunsaturated to saturated fatty acids (P/S ratio) of the diet. Diets with P/S ratios of 0.25-0.4 are accompanied by elevations of low density lipoprotein (LDL) cholesterol, whereas diets with a P/S ratio of 2.5 produce no significant changes in cholesterol levels. On the low P/S ratio diets, the structure, composition, and interaction with cultured fibroblasts of LDL are not significantly changed. Plasma high density lipoprotein (HDL) cholesterol levels remain constant, but HDL2 increase relative to HDL3. In the present study, not only dietary cholesterol but also total dietary fat was altered. Six normal young men were fed a basal diet consisting of 18% protein, 51% carbohydrate, and 30% fat, containing 250 mg/day cholesterol. After 2 weeks, an experimental diet consisting of 18% protein, 42% carbohydrate, and 39% fat, containing 1760 mg/day cholesterol, was fed for 4 weeks. The P/S ratios of both diets were about 0.4. Plasma samples were taken twice during each dietary period from 12- to 14-h-fasted subjects and analyzed for their contents of lipoprotein lipids. Plasma levels of LDL and HDL cholesterol increased by 30 and 13 mg/dl, respectively; total and very low density lipoprotein (VLDL) triglyceride concentrations were unaltered. The plasma concentrations of apoproteins (apo) B, E. and A-I, but not A-II, were elevated. Plasma samples also were studied by zonal ultracentrifugation, gel permeation column chromatography, and Pevikon electrophoresis. Although on zonal ultracentrifugation the total concentrations of LDL were increased, the flotation properties and chemical compositions of LDL were not changed. By contrast, HDL2 and HDL3L concentrations increased, and HDL2 became enriched with cholesteryl esters. On gel permeation chromatography, with the subjects on the basal diet, plasma cholesterol eluted in two peaks, corresponding to LDL and HDL. The sizes of the peaks increased on the experimental diet. ApoE eluted in two peaks: one at the leading edge of LDL (corresponding to VLDL or IDL) and the other in the area between LDL and HDL, corresponding to HDLC. On the experimental diet, the apoE peak between LDL and HDL increased. On Pevikon electrophoresis apoE migrated between the LDL and HDL bands. This apoE peak was increased on the experimental diet. These findings suggest that increasing the concentrations of both dietary cholesterol and total fat can increase the levels of plasma LDL, HDL2, and HDLC in fasting normal subjects. Thus, the concentrations of some putatively atherogenic as well as antiatherogenic lipoproteins increased in plasma, and the apparent paradox between the epidemiological and metabolic behaviors of some lipoproteins remains. Clearly, more work is needed to resolve the roles of various lipoproteins in plasma in atherosclerosis.

Lipoprotein levels in morbidly obese patients with massive, surgically-induced weight loss

Abnormalities in lipoprotein metabolism are among the risk factors for atherosclerotic cardiovascular disease frequently present in patients with morbid obesity. We have examined the effects of dietary restriction induced by gastric bypass surgery on plasma lipoprotein levels in 22 morbidity obese patients. Operation induced weight loss in all patients. Postoperatively (12 +/- 7 mo), triglycerides decreased from 146.4 +/- 67 (mean +/- S.D. before operation) to 104 +/- 44 mg/dl (p less than 0.01), total cholesterol decreased from 187 +/- 52 to 166 +/- 39 mg/dl (p less than 0.025), LDL cholesterol levels decreased from 119 +/- 42 to 104 +/- 36 mg/dl (p less than 0.038), and HDL cholesterol levels increased from 40.1 +/- 10.1 to 45.2 +/- 9.5 mg/dl (p less than 0.012). HDL cholesterol to LDL cholesterol ratio increased from 0.37 +/- 0.13 to 0.48 +/- 0.21 (p less than 0.01). The results of apo A-1, A-2 and B determinations (n = 12) paralleled the changes in lipoprotein levels. Apo A1/Apo A2 ratio increased suggesting an increase in the concentration of HDL2. We conclude that weight loss following gastric bypass surgery is associated with favorable changes in lipoprotein metabolism which may help prevent or delay the development of atherosclerotic cardiovascular disease. The mechanism responsible for the lipoprotein changes remains to be determined.

Antigenic mapping of human low density lipoprotein with monoclonal antibodies

Monoclonal anti-LDL antibodies were produced in a mouse spleen-myeloma system and purified by affinity chromatography on insolubilized low density lipoprotein (LDL). Five antibodies with different specificities could be distinguished by their immunoreactivities with chemically modified LDL preparations, and by their competition for binding to LDL. One of the antibodies inhibited the binding of (125)I-labeled LDL to the apoB,E receptors of cultured human fibroblasts. The same degree of inhibition was achieved using isolated Fab fragments. This antibody may bind to an antigenic site located near the cellular binding site of LDL-apoB.-Tikkanen, M. J., R. Dargar, B. Pfleger, B. Gonen, J. M. Davie, and G. Schonfeld. Antigenic mapping of human low density lipoprotein with monoclonal antibodies.

The effect of short-term feeding of a high carbohydrate diet on HLD subclasses in normal subjects

Plasma HDL concentrations are effected by several perturbations, including certain dietary manipulations. In this study we have examined the effects of a one week ingestion of an isocaloric, fat-free, high-carbohydrate diet (CHO greater than 80% of calories) and the concentrations and compositions of plasma HDL subclasses. Eleven healthy normolipidemic volunteers (6 females, 5 males) took part in this study. Blood samples for lipoprotein analysis were drawn before and at the end of the dietary period and analyzed for lipoprotein lipid and apoprotein concentrations. Lipoproteins also were characterized by zonal ultracentrifugation. Our results show the following significant changes at the end of the dietary period: plasma concentrations of VLDL-TG, VLDL-cholesterol and total VLDL mass increased, whereas plasma concentrations of LDL-cholesterol, LDL mass and HDL-cholesterol and HDL mass, decreased. Plasma concentrations of apoprotein A1 decreased (from 133.3 +/- 7.7 to 108.1 +/- 8.6; mean +/- S.E.M., p less than 0.0004), and apoprotein A2 concentrations remained unchanged. This resulted in a drop in plasma ratio of ApoA1/ApoA2 (p less than 0.03). Since it has been shown that ApoA1/ApoA2 ratio is higher in HDL2 than HDL3, we examined the concentrations of these two subfractions, employing rate-zonal ultracentrifugation for their isolation. One week of ingestion of the study diet was followed by consistent decreases in HDL2 mass (from 84 +/- 15 to 44 +/- 16 mg/dl, mean +/- S.E.M.), with inconsistent changes in HDL3 mass, (from 254 +/- 18 to 222 +/- 13 mg/dl) resulting in significant decreases in HDL2/HDL3 mass ratio. Lipid analyses of these subfractions did not demonstrate major compositional changes. The alterations noted could be due to decreased HDL production, at least in part, but alterations in the interconversions of lipoproteins also could have played a role. The falls in HDL2 on a diet which should be "antiatherogenic" illustrate the difficulty of assessing the atherogenicity of any given diet solely by the changes it produces in the levels of circulating lipoproteins.

Nonenzymatic glycosylation of low density lipoproteins in vitro. Effects on cell-interactive properties

Atherosclerosis occurs at an accelerated rate in patients with diabetes mellitus. Since some proteins undergo nonenzymatic glycosylation in diabetic patients and because certain chemical modifications of low density lipoproteins produced alterations in their interactions with certain cultured cells, a fact that may be relevant to atherogenesis, we investigated the effect of in vitro glycosylation on cell-related properties of low density lipoproteins. Glycosylation was carried out by incubating LDL (1-10 mg LDL-protein/ml) with glucose (0-100 mM) in 0.5 M phosphate buffer, pH 8.0, at 37 degrees C. The amount of glucose incorporated into LDL after 1-2 wk of incubation was estimated to be in the range of 1-10 mol/mol LDL-protein. Amino acid analysis of glycosylated LDL showed that glucose was covalently bound to lysine residues. In studies with cultured human fibroblasts, glycosylated LDL was internalized and degraded significantly less than control LDL, in proportion to the estimated degree of glycosylation (12% of control for the most extensively glycosylated LDL). Glycosylation of LDL also impaired significantly its ability to stimulate cholesteryl ester synthesis by cultured fibroblasts. Glycosylated LDL did not stimulate cholesteryl ester synthesis in rat peritoneal macrophages. If glycosylation of LDL occurs in diabetic patients, some pathophysiologic consequences related to the increased incidence of atherosclerosis in these patients may result.

Recovery after muscular fatigue in hemiparesis

Setchenov showed in 1903 that the amount of work he could perform with his right arm after a pause, during which he had worked with his nonfatigued left arm was greater than if he had rested passively between bouts. Asmussen and Mazin have shown that recuperation after local muscle fatigue was influenced by a central nervous factor. In this paper 10 stroke patients were examined and the muscular activity of the deltoid was measured by means of EMG. The intact deltoid behaved according to Setchenov's observation. In 4 patients the diverting activity did not have any beneficial effect on the paretic muscle. It is assumed that in some of the stroke patients the brain damage affects the facilitatory centers which are needed for the recuperation after muscular fatigue.