Regional and temporal progression of reactive astrocytosis in the brain of the myelin mutant taiep rat

Reactive astrocytosis in taiep rats was shown by glial fibrillary acidic protein (GFAP) immunoreactivity measured by means of enzyme-linked immunosorbent assay and indirect immunofluorescence. Increased GFAP immunoreactivity was first observed in the brainstem of 15-day-old taiep rats and was widespread throughout all brain regions at 6 months of age. Characteristically, astrocytes were hypertrophic and displayed strong GFAP fluorescence. The pattern of these reactive cells may correlate with the process of dysmyelination in the taiep rat.

O-Glycosylation in sprouting neurons in Alzheimer disease, indicating reactive plasticity

Reactive plasticity, including axonal and dendritic sprouting and reactive synaptogenesis, has been proposed to contribute to the pathogenesis of several neurological disorders. This work was aimed at identifying the possible role of protein glycosylation in the brain from patients with Alzheimer disease (AD), using lectin histochemistry, as determinants of reactive plasticity. Results indicate an increase in the production of cryptic O-glycosidically linked proteins (NeuAcalpha2,6 Galbeta1,3GalNAcalpha1,0 Ser/Thr or sialyl-T-antigen) in neuritic sprouting in AD brains as determined by positive labeling with Amaranthus leucocarpus (ALL, T-antigen-specific) and Macrobrachium rosenbergii (MRL, specific for NeuAc5,9Ac2) lectins. Immunohistochemistry indicated that lectin staining was specific for the synaptic sprouting process (meganeurites) in AD. These results were confirmed using anti-synaptophysin and anti-GAP 43 antibodies, which recognized meganeurites and dystrophic neurites around amyloid-beta deposits. In normal control brains, labeling with the aforementioned lectins was restricted to microvessels. Control experiments with neuraminidase-treated brain samples revealed positivity to the lectin from Arachis hypogaea (PNA), which is specific for galactose. Our results suggest specific O-glycosylation patterns of proteins closely related to neuronal plasticity in AD.

Altered glycosylation pattern of proteins in Alzheimer disease

Post-translational modifications due to glycosylation of proteins in human brains from patients with Alzheimer disease (AD) were analyzed using lectin histochemistry. Results indicate a significant increase in the production of O-glycosylated (containing Galbeta1,3GalNAc alpha1,0 Ser/Thr or GalNAc alpha1,0 Ser/Thr) proteins in neuritic plaques and neurofibrillary tangles which are the major histopathological hallmarks of AD brains. These alterations were determined by positive labelling with lectins obtained from Amaranthus leucocarpus (ALL) and Macrobrachium rosenbergii (MRL) respectively. Immunohistochemistry indicated that the lectin-staining labelled specifically both neurofibrillary tangles and neuritic plaques. In contrast, lectins labelling was restricted to microvessels in normal control brains. These results provide evidence that modifications of the specific glycosylation patterns are closely related with the presence of the hallmark lesions of this disease, suggesting that an abnormal enzymatic processing of proteins may be an early event in the neuronal degeneration which characterises AD.

Interaction of apolipoprotein[a] with apolipoproteinB-100 Cys3734 region in lipoprotein[a] is confirmed immunochemically

Monospecific polyclonal antibodies (MPAbs) to apoB-100 regions Cys3734 and Cys4190 were isolated by affinity chromatography using the synthetic polypeptides, Q3730VPSSKLDFREIQIYKK3746 and G4182IYTREELSTMFIREVG4198, respectively, coupled to a hydrophilic resin. Molecular modeling and fluroescence labeling studies have suggested that Cys67 located in kringle type 9 (LPaK9, located between residues 3991 and 4068 of the apo[a] sequence inferred by cDNA) of the apo[a] molecule is disulfide linked to Cys3734 of apoB-100 in human lipoprotein[a] (Lp[a]). This possibility has been further explored with MPAbs. Four species of MPAbs directed to a Cys3734 region of apoB-100 (3730-3746) were isolated from goat anti-human LDL serum by a combination of synthetic peptide (Q3730VPSSKLDFREIQIYKK3746) affinity chromatography and preparative electrophoresis (electrochromatography). MPAbs to the Cys4190 region of apoB-100, a second or alternative disulfide link-site between apo[a] and apoB-100, were also isolated using a synthetic peptide (G4182IYTREELSTMFIREVG4198) affinity resin. Results of immunoassays showed that binding of these four MPAbs to Lp[a] was significantly lower than to LDL. In contrast, MPAbs to the apoB-100 region 4182-4198 which contains Cys4190, a second or alternative disulfide link-site between apo[a] and apoB-100, displayed a less significant difference in binding to Lp[a] and LDL. These results provide additional evidence that the residues 3730-3746 of apoB-100 interact significantly with apo-a- in Lp-a-, and that Cys3734 is a likely site for the disulfide bond connecting apo[a] and apoB-100.

Human Lp(a): regions in sequences of apoproteins similar to domains in signal transduction proteins

The major apoproteins of Lp(a)--apo(a) and apo B-100--are linked by only one intermolecular disulfide bond. This linkage has been suggested to be located between apo(a) Cys4057 and apo B-100 Cys3734. Several studies, however, have suggested other noncovalent interactions between different regions of apo(a) and apo B-100. One possible mechanism for these interactions may involve the apo(a) proline-rich interkringle regions that share sequence similarities with the proline-rich regions of Src homology 3 (SH3) domain-binding proteins such as 3BP-1. SH3 and SH2 domains, and their respective ligands, proline-rich regions, and phosphotyrosine motifs, are noncatalytic segments common to signal transduction proteins. Therefore, we used sequence comparison algorithms and molecular modeling programs to identify corresponding SH3 and SH2 candidate regions as well as potential phosphotyrosine sites in the apo B-100 sequence. Six SH2 and 16 SH3 candidate regions, along with 21 potential phosphotyrosine sites, are contained in the apo B-100 sequence. In Lp(a), these regions of apo B-100 may be involved in the noncovalent, protein-protein interactions between apo(a) and apo B-100. The presence of candidate SH3 and SH2 regions in apo B-100, and potential phosphotyrosine sites in apo B-100, apo(a), and apo A-I, suggests an alternative signaling pathway unrelated to the known B/E receptor.

Evidence that apoB-100 of low-density lipoproteins is a novel Src-related protein kinase

Protein-tyrosine kinases of signal transduction pathways occur and function intracellularly. In contrast, the low-density lipoprotein (LDL) particle circulates in plasma, where its function is to solubilize and transport lipid. Recently, several reports showed that LDL may have a role in signal transduction. We have identified a region in the apoB-100 primary structure which shows similarity to Src-homology-1 (SH1) domains, the kinase region of protein-tyrosine kinases. Results obtained in protein kinase assays of highly purified LDL showed that only the apoB-100 was phosphorylated, suggesting that apoB-100 has the capacity to undergo autophosphorylation like known protein-tyrosine kinases. Phosphorylation was not observed for any other apolipoprotein in LDL or for any component of high-density lipoprotein and lipoprotein [a]. Our results suggest that apoB-100 may be a novel and functional member of the src protein kinase family.

Long distance runners and body-builders exhibit elevated plasma levels of lipoprotein(a)

A one-point cross-sectional study of 20 sedentary individuals, 20 low-aerobic athletes (body-builders), and 20 high-aerobic athletes (long distance, endurance runners) was conducted in Mexico City, Mexico to determine the influence of these diverse life-styles on the plasma levels of Lp(a). Only non-obese male subjects, aged 23-33, who were nonsmokers, non-alcoholics, and had never used anabolic steroids were included in this study. Blood samples were drawn 24 h following the last period of physical activity, and after a 12-14-h fast-period and a 15-min sitting-rest. Plasma levels of Lp(a) and other parameters, including postheparin lipoprotein lipase (LPL) and hepatic lipase (HL) activities, triglycerides (TG), total cholesterol (TC), LDL cholesterol (LDL-C), and HDL cholesterol (HDL-C), as well as % body fat and muscle mass, and maximum aerobic capacity (VO2max) were measured to determine possible correlations with Lp(a) and to serve as convenient internal standards. Mean Lp(a) concentrations were significantly higher in the runners (52 +/- 19 mg/dl) than in the body-builders (40 +/- 6.4 mg/dl, P < 0.05) and the sedentary subjects (24 +/- 5 mg/dl, P < 0.001). Positive correlations between Lp(a) and Vo2max (P < 0.001), HDL-C (P < 0.005) and HDL2-C subfraction (P < 0.005), and a negative correlation with TG were determined. Agglomerative cluster methods suggested three close-distance clusters and a fourth cluster which is composed of four runners who exhibited low LDL-C/HDL-C and high LPL/HL ratios, high mean Lp(a), HDL2-C, and Vo2max levels, but low TG levels. These data show that some individuals who maintain a life-style of very high level physical exertion may have remarkably elevated plasma Lp(a) concentrations. The highly increased concentrations of Lp(a) in high exercise athletes may represent a normal metabolic response to repeated small tissue injuries resulting from frequent and prolonged large muscle movement.

Recent advances in lipoprotein and atherosclerosis research at Baylor College of Medicine. Apolipoprotein B, lipoprotein[a], and transplantation arteriopathy

A multidisciplinary team approach with focused objectives characterizes research at Baylor College of Medicine into the causes, prevention, and treatment of atherosclerotic disease. Current clinical activities range from programs to modify lifestyle for the primary prevention of coronary artery disease to a large, angiographically monitored lipid-lowering trial. In basic research, much attention has been focused on the plasma lipoproteins and their roles in atherogenesis. The current review highlights recent advances in ongoing basic research involving 1) apolipoprotein (apo) B, whose form apo B-100 serves as a ligand for the low-density lipoprotein receptor; 2) lipoprotein[a], elevated plasma levels of which are predictive of atherosclerotic disease; and 3) transplantation arteriopathy, which impedes long-term survival of cardiac transplant recipients.

Identification and quantification of apolipoproteins in addition to apo[a] and apo B-100 in human lipoprotein[a]

The protein moiety of Lp[a] is widely believed to consist of one molecule of apo B-100 and one molecule of apo[a] per particle, linked by at least one disulfide bond. In this study we have re-examined the composition of Lp[a] to determine if other less abundant apolipoproteins might be present. Analysis of Lp[a] by sodium dodecyl sulfate-polyacrylamide electrophoresis under reducing conditions showed bands corresponding to < 200 kD but > 50 kD, 40 kD, 26 kD, 23 kD and 9 kD when stained with silver. Western immunoblot analysis of three preparations of Lp[a] revealed the presence of apoE and apoD. Enzyme-linked immunoassays were used to quantify apoA-I, apoA-II, apoC-I, apoC-II, apoC-III, apoE and apo B-100 in Lp[a] and autologous LDL isolated from three healthy males. There is a significant amount of apoA-I in the Lp[a], although the levels varied widely among the different samples. ApoE concentrations were consistent in the three Lp[a] samples and were between 22 and 26% of relative apo B-100 concentrations. Relatively minor amounts of apoA-II and no apoCs were detectable in the three Lp[a] preparations. In contrast, the autologous LDL preparations contained relatively higher amounts of apoA-I, apoA-II, apoE, apoC-I, apoC-II and apoC-III. The identity of the multiple bands corresponding to < 200 kD and > 54 kD and 9 kD is not established.

Inverse masticatory muscle activity due to syringobulbia

The clinical, radiological, and electrophysiological data of a 25-year-old woman with "inverse masticatory muscle activity" due to syringobulbia is presented. This uncommon brain stem syndrome may be due to a disturbance in central programming of mastication.

Comparison of ligand-binding sites of modeled apo[a] kringle-like sequences in human lipoprotein[a]

Human lipoprotein[a] contains at least two high-molecular-weight, disulfide-linked apolipoproteins, apo[a] and apo B-100. Apo[a] is a highly glycosylated, hydrophilic apoprotein that somewhat resembles plasminogen by containing an extended kringle domain and a carboxyl-terminal serine protease domain. The apo[a] kringle domain is composed of 11 distinct kringle types. Ten of these display high sequence homology to plasminogen kringle 4 (PGK4). The crystallographic coordinates for PGK4 were used to generate three-dimensional molecular models of the apo[a] kringle types, and the lysine-binding region of PGK4 was used to compare the different potential receptor-ligand and ligand-binding sites contained in each different PGK4-like kringle of apo[a]. A receptor-ligand site can be proposed for each kringle type. Potential serine protease cleavage sites, containing arginine-threonine and threonine-arginine, are located on the surface of the kringles. The ligand-binding site of one apo[a] kringle model is almost identical to that of PGK4 and may be a lysine-binding site of apo[a]. Four other apo[a] kringle models appear to have structurally similar lysine-binding sites, but with differences that may influence ligand-polypeptide specificity. Five apo[a] kringle models have ligand-binding sites that probably do not bind lysine; one of these is the highly repeated kringle in the known apo[a] polymorph.

Proposed mechanisms for binding of apo[a] kringle type 9 to apo B-100 in human lipoprotein[a]

The protein component of human lipoprotein[a] consists primarily of two apolipoproteins, apo[a] and apo B-100, linked through a cystine disulfide(s). In the amino acid sequence of apo bd, Cys4057 located within a plasminogen kringle 4-like repeat sequence (3991-4068) is believed to form a disulfide bond with a specific cysteine residue in apo B-100. Our fluorescence-labeling experiments and molecular modeling studies have provided evidence for possible interactions between this apo[a] kringle type and apo B-100. The fluorescent probe, fluorescein-5-maleimide, was used in parallel experiments to label free sulfhydryl moieties in lipoprotein[a] and low-density lipoprotein (LDL). In apo B-100 of LDL, Cys3734 was labeled with the probe, but this site was not labeled in autologous lipoprotein[a]. The result strongly implicates Cys3734 of apo B-100 as the residue forming the disulfide linkage with Cys4057 of apo[a]. To explore possible noncovalent interactions between apo B-100 and apo[a], the crystallographic coordinates for plasminogen kringle 4 were used to generate molecular models of the apo[a] kringle-repeat sequence (3991-4068, LPaK9), the only plasminogen kringle 4 type repeat in apo[a] having an extra cysteine residue not involved in an intramolecular disulfide bond. The Cys4057 residue (henceforth designated as Cys67 in the LPaK9 sequence) is believed to form an intermolecular disulfide bond with a cysteine of apo B-100. In computer graphics molecular models of LPaK9, Cys67 is located on the surface of the kringle near the lysine ligand binding site. Selected segments of the LDL apo B-100 sequence that contain free sulfhydryl cysteines were subjected to energy minimization and docking with the ligand binding site and adjacent regions of the LPaK9 model. In the docking experiments, apo B-100 segment 3732-3745 (PSCKLDFREIQIYK) displayed the best fit and the largest number of van der Waals contacts with models of LPaK9. Other apo B-100 peptides with sulfhydryl cysteine were found to be less compatible when minimized with this kringle. These results support and extend previously suggested mechanisms for a complex interaction between apo[a] and apo B-100 that involve more than a simple covalent disulfide bond.

Method for calculating 3-D coordinates from molecular stereograms

The three-dimensional coordinates for the alpha-carbon atoms of crambin and basic pancreatic trypsin inhibitor (BPTI) were determined from the respective alpha-carbon trace stereograms using an improved Simplex algorithm. This algorithm was used in a two-step process to estimate the z-coordinate values. In one approach, an average interatomic distance value, an approximate viewing angle, and a table of digitized values for xleft, yleft and xright, yright are provided in the first step. In the second step, the z-coordinate values are derived by varying z to minimize the bond distance error (Rossmann and Argos, 1980). In another approach, only a reference bond distance table is provided along with the table of xleft, yleft and xright, yright digitized values. In the first step, the viewing angle (phi), a combined scale and viewing distance parameter (q), a rotational angular distortion from digitizing and/or photocopying (z), and translational distortion factors (xerr and yerr) are calculated. In the second step, the z-coordinate values are varied to minimize the bond distance error. RMS difference values of less than 1.5 A were obtained for both crambin and BPTI alpha-carbon atoms.

Sialic acid content of human low density lipoproteins affects their interaction with cell receptors and intracellular lipid accumulation

Low density lipoproteins (LDL) isolated from the plasma of patients with angiographically demonstrable coronary heart disease (CHD) induced accumulation of triglycerides, free cholesterol, and cholesteryl esters in cultured macrophages, smooth muscle cells, and endothelial cells derived from uninvolved intima of human aorta, but not in skin fibroblasts or hepatoma cells. The sialic acid content of LDL from CHD patients was 40-75% lower than that from healthy donors. There was a negative correlation between LDL sialic acid content and the LDL-induced accumulation of total intracellular cholesterol. Neuraminidase treatment of LDL from normal healthy donors produced sialic acid-depleted LDL (Ds-LDL) which was able to stimulate intracellular lipid accumulation. Neuraminidase treatment of LDL from CHD patients further increased its capacity to induce intracellular lipid accumulation. Sialic acid-poor LDL isolated by affinity chromatography of LDL from CHD patients induced a 2- to 4-fold increase of free and esterified cholesterol in human intimal smooth muscle cells. Binding, uptake, and degradation of 125I-labeled Ds-LDL by macrophages and endothelial cells were 1.5- to 2-fold higher than for native LDL. Binding and uptake of Ds-LDL was inhibited 64-93% by the addition of 20-fold excess acetylated LDL (Ac-LDL); in the inverse experiment, the level of inhibition was 35-54%. These data indicate that a sialic acid-poor form of LDL isolated from CHD patients can interact with both native and scavenger LDL receptors. A sialic acid-poor form of LDL may be a naturally occurring ligand that interacts with the scavenger receptor(s) on macrophages and endothelial cells.

A structural assessment of the apo[a] protein of human lipoprotein[a]

Apolipoprotein[a], the highly glycosylated, hydrophilic apoprotein of lipoprotein[a] (Lp[a]), is generally considered to be a multimeric homologue of plasminogen, and to exhibit atherogenic/thrombogenic properties. The cDNA-inferred amino acid sequence of apo[a] indicates that apo[a], like plasminogen and some zymogens, is composed of a kringle domain and a serine protease domain. To gain insight into possible positive functions of Lp[a], we have examined the apo[a] primary structure by comparing its sequence with those of other proteins involved in coagulation and fibrinolysis, and its secondary structure by using a combination of structure prediction algorithms. The kringle domain encompasses 11 distinct types of repeating units, 9 of which contain 114 residues. These units, called kringles, are similar but not identical to each other or to PGK4. Each apo[a] kringle type was compared with kringles which have been shown to bind lysine and fibrin, and with bovine prothrombin kringle 1. Apo[a] kringles are linked by serine/threonine- and proline-rich stretches similar to regions in immunoglobulins, adhesion molecules, glycoprotein Ib-alpha subunit, and kininogen. In comparing the protease domains of apo[a] and plasmin, apo[a] contains a region between positions 4470 and 4492 where 8 substitutions, 9 deletions, and 1 insertion are apparent. Our analysis suggests that apo[a] kringle-type 10 has a high probability of binding to lysine in the same way as PGK4. In the only human apo[a] polymorph sequenced to date, position 4308 is occupied by serine, whereas the homologous position in plasmin is occupied by arginine and is an important site for proteolytic cleavage and activation. An alternative site for the proteolytic activation of human apo[a] is proposed.

Subarachnoid and intramedullary cysts secondary to epidural anesthesia for gynecological surgery

Three women who received epidural anesthesia for gynecological surgery developed spinal arachnoiditis leading to subarachnoid cysts and cord cavitation. MRI was useful to show the subarachnoid and intramedullary cysts, as well as to monitor lesion extent and progress. Associated MRI findings were a Chiari anomaly in 1 case and a tethered cord in another. Two cases underwent surgery: 1 improved, but the other suffered progressive neurological deterioration. Although the 3rd patient had no treatment, there was spontaneous reduction in cavity size and clinical improvement. Careful handling of this procedure is urged to avoid such severe complications in young mothers.

A Double-Blind, Parallel, Comparative Evaluation of Amlodipine vs. Captopril in the Monotherapeutic Treatment of Mild and Moderate Essential Hypertension

A double-blind, parallel, comparative study of the antihypertensive efficacy and safety of once-daily oral doses of amlodipine (5-10 mg/day) vs. twice-daily oral doses of captopril (25-50 mg twice daily) in adult patients with mild or moderate essential hypertension (supine diastolic blood pressure of 95-115 mm Hg) was undertaken in two hospital centers. Interim analysis of data from 40 patients shows that amlodipine and captopril both significantly (p < 0.05) reduced blood pressure compared with baseline. Nineteen of 21 (90.5%) amlodipine-treated patients and 15 of 19 (78.9%) captopril-treated patients had their diastolic blood pressure "normalized" (< 90 mm Hg) with mean final doses of 8.2 and 76.7 mg/day, respectively. At the final visit, there were no statistically significant differences between the two treatment groups in either mean supine or standing blood pressure. Minor nonsignificant changes in standing heart rate were observed in both treatment groups. Seven of the 21 amlodipine-treated patients and 3 of the 19 captopril-treated patients reported adverse experiences. No patients in either treatment group discontinued due to adverse events; one patient in the amlodipine group required a dose reduction. These interim data indicate that the overall efficacy and safety profiles of these two drugs are comparable.

Polymorphic forms of human apolipoprotein[a]: inheritance and relationship of their molecular weights to plasma levels of lipoprotein[a]

The plasma concentration of human lipoprotein[a], Lp[a], is highly correlated with coronary artery disease. The protein moiety of Lp[a], apoLp[a], consists of two apoproteins, apo[a] and apoB-100, linked by one or more disulfide bonds(s). Apo[a], the protein unique to Lp[a], exists in polymorphic forms that exhibit different apparent molecular weights (Mr). Polyacrylamide gel electrophoresis in sodium dodecyl sulfate followed by immunoblotting was used to separate and visualize these different forms and to determine the polymorphic pattern of apo[a] in the plasma samples of 692 individuals. A total of 11 different polymorph bands ranging in Mr from 419 kD to 838 kD could be resolved, but only 1 or 2 bands were present per individual. The polymorphic band pattern for an individual was assigned to 1 of the 66 different phenotype designations representing the total number of possible single- and double-band combinations of the 11 detectable bands. All 11 of the possible single-band phenotypes but only 32 of the 55 possible double-band phenotypes were represented. There were 412 plasma samples (59.5%) that contained a single band, 274 (39.6%) contained two bands, and only 6 (0.9%) had no detectable apo[a] band. A highly significant inverse correlation was found between the Mr of the band(s) present and the plasma apoLp[a] concentration (r = -0.461; rho = 0.0001). The correlation was better between apoLp[a] and single-band (r = -0.495; rho = 0.0001) than double-band (r = -0.382; rho = 0.0001) phenotypes. Of the 274 individuals exhibiting double-band phenotypes, the lower Mr band was more intense in 141 (51.4%), the two bands were equally intense in 85 (31.0%), while the higher Mr band was more intense in 48 (17.5%). Based upon the hypothesis that apo[a] polymorphism is controlled by different alleles at a single locus, the frequency of the 11 alleles determined from the observe phenotypes (low Mr----high Mr) was: band 1) 419 kD, 0.00875; band 2) 489 kD, 0.00510; band 3) 536 kD, 0.0555; band 4) 553 kD, 0.0758; band 5) 613 kD, 0.135; band 6) 680 kD, 0.0824; band 7) 705 kD, 0.104; band 8) 742 kD, 0.151; band 9) 760 kD, 0.246; band 10) 796 kD, 0.128; band 11) 838 kD, 0.00802. The observed distribution of phenotypes in the population was compared by chi-square analysis to that predicted on the basis of simple Mendelian inheritance, and the hypothesis was rejected (chi 2 = 921.7; rho less than 0.001). Significantly, the singleband phenotypes are over-represented in the population compared to that predicted.(ABSTRACT TRUNCATED AT 400 WORDS)