Showing papers by "University of Texas Southwestern Medical Center published in 1988"

The presence of malfolded proteins in the endoplasmic reticulum signals the induction of glucose-regulated proteins

Abstract: Two glucose-regulated proteins, GRP78 and GRP94, are major constituents of the endoplasmic reticulum (ER) of mammalian cells. These proteins are synthesized constitutively in detectable amounts under normal growth conditions; they can also be induced under a variety of conditions of stress including glucose starvation and treatment with drugs that inhibit cellular glycosylation, with calcium ionophores or with amino-acid analogues. Unlike the closely-related heat shock protein (HSP) family, the GRPs are not induced significantly by high temperature. Recently, GRP78 has been identified as the immunoglobulin heavy chain binding protein (BiP) (ref. 5 and Y.K. et al., in preparation) which binds transiently to a variety of nascent, wild-type secretory and transmembrane proteins and permanently to malfolded proteins that accumulate within the ER. We have tested the hypothesis that the presence of malfolded proteins may be the primary signal for induction of GRPs by expressing wild-type and mutant forms of influenza virus haemagglutinin (HA) in simian cells. Only malfolded HAs, whose transport from the ER is blocked, induced the synthesis of GRPs 78 and 94. Additional evidence is presented that malfolding per se, rather than abnormal glycosylation, is the proximal inducer of this family of stress proteins.

Effect of Dietary Stearic Acid on Plasma Cholesterol and Lipoprotein Levels

Abstract: We studied the metabolic effects of stearic acid (18:0) on plasma lipoprotein levels in 11 subjects during three dietary periods of three weeks each. The three liquid-formula diets, which were used in random order, were high in palmitic acid (16:0), stearic acid, and oleic acid (18:1), respectively. Caloric intakes were the same during the three periods. As compared with the values observed when the subjects were on the high-palmitic-acid diet, plasma total cholesterol decreased by an average of 14 percent during consumption of the high-stearic-acid diet (P less than 0.005) and by 10 percent during consumption of the high-oleic-acid diet (P less than 0.02). Low-density lipoprotein cholesterol levels fell by 21 percent in subjects on the high-stearic-acid diet (P less than 0.005) and by 15 percent in subjects on the high-oleic-acid diet (P less than 0.005). No significant differences were observed in the plasma levels of triglycerides or high-density lipoprotein cholesterol among the three diets. Measurements of the intestinal absorption of palmitic, stearic, and oleic acids revealed essentially complete absorption of each during the three dietary periods. The oleic acid content of plasma triglycerides and cholesteryl esters increased significantly during the high-stearic-acid period, suggesting that stearic acid is rapidly converted to oleic acid. We conclude that stearic acid appears to be as effective as oleic acid in lowering plasma cholesterol levels when either replaces palmitic acid in the diet.

Regulation of antibody isotype secretion by subsets of antigen-specific helper T cells.

Abstract: The regulation of the subclass of immunoglobulin secreted by B cells has been studied in vitro in polyclonal systems using mitogens, such as lipopolysaccharide (LPS), to bypass the requirement for cognate interaction between antigen-specific T and B cells. In these systems, interleukin-(IL)-4 induces the secretion of IgG1 (ref. 1) and IgE (ref. 2); IL-5 enhances the secretion of IgA, and interferon-gamma (IFN-gamma) enhances the secretion of IgG2a (ref. 5). Clones of murine TH cells can be divided into two subsets, TH1 and TH2 (ref. 6). Both subsets synthesize IL-3 and granulocyte-monocyte colony-stimulating factor (GM-CSF), but only TH1 clones produce IL-2, IFN-gamma, and lymphotoxin (LT) and TH2 clones produce IL-4 and IL-5 (ref. 7). We have examined the role of clones of antigen-specific TH1 and TH2 cells in the regulation of the subclasses of IgG antibody secreted by antigen-specific B cells. Our results show that both types of TH cells induce the secretion of IgM and IgG3, whereas clones of TH1 and TH2 cells specifically induce antigen-specific B cells to secrete IgG2a and IgG1, respectively. We also demonstrate that regulation of commitment to the secretion of a particular IgG isotype occurs in two distinct stages: cognate interaction between T and B cells and interaction between T-cell-derived lymphokines and B cells.

HMG-CoA reductase inhibitors for treatment of hypercholesterolemia.

Abstract: THE recent introduction of a unique class of cholesterol-lowering drugs offers new promise for the treatment of hypercholesterolemia. These drugs are inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, the rate-limiting enzyme in the synthesis of cholesterol. Relatively low doses of these agents will reduce plasma cholesterol levels markedly, and in short-term studies, they have not been found to produce serious side effects. Thus, in 1987 the Food and Drug Administration approved one HMG-CoA reductase inhibitor — lovastatin. If reductase inhibitors prove to be free of long-term adverse effects, they will undoubtedly be used widely for treating hypercholesterolemia. This review will examine . . .

Prevention of venous thromboembolism in general surgical patients. Results of meta-analysis.

Abstract: The results of randomized clinical trials evaluating commonly used methods of deep vein thrombosis (DVT) prophylaxis in moderate- and high-risk general surgery patients were pooled to obtain an unbiased estimate of efficacy and risks. Low-dose heparin (LDH), dextran, heparin-dihydroergotamine (HDHE), intermittent pneumatic compression (IPC), and graded elastic stockings significantly reduced the incidence of DVT; aspirin was ineffective. In contrast to other methods, elastic stockings have not been adequately studied to determine their value in reducing DVT in high-risk patients, such as those with malignancy. Only LDH and dextran were studied in numbers of patients sufficient for demonstrating a clear reduction in pulmonary embolism (PE). In comparison studies, LDH was superior to dextran in preventing DVT, but the two agents were equivalent in protecting against PE. Although HDHE was marginally better than LDH in preventing DVT, it appeared to have no advantage in preventing PE--at least in moderate-risk patients. The incidence of major hemorrhage was not increased with any of the prophylactic agents. However, wound hematomas occurred significantly more frequently with LDH, an effect noted in the pooled data from double-blind and open trials. In comparison trials with LDH, both dextran and HDHE had significantly fewer wound hematomas. LDH administered every 8 hours appeared more effective in reducing DVT than LDH administered every 12 hours; the incidence of wound hematomas was equivalent with both regimens.

Dexamethasone therapy for bacterial meningitis

Abstract: We enrolled 200 infants and older children with bacterial meningitis in two prospective double-blind, placebo-controlled trials to evaluate the efficacy of dexamethasone therapy in addition to either cefuroxime (Study 1) or ceftriaxone (Study 2). Altogether, 98 patients received placebo and 102 received dexamethasone (0.15 mg per kilogram of body weight every six hours for four days). At the beginning of therapy, the clinical and demographic characteristics of the patients in the treatment groups were comparable. The mean increase in the cerebrospinal fluid concentration of glucose and the decreases in lactate and protein levels after 24 hours of therapy were significantly greater in those who received dexamethasone than in those who received placebo (glucose, 2.0 vs. 0.4 mmol per liter [36.0 vs. 6.9 mg per deciliter], P less than 0.001; lactate, 4.0 vs. 2.1 mmol per liter [38.3 vs. 19.8 mg per deciliter], P less than 0.001; and protein, 0.64 vs. 0.25 g per liter [64.0 vs. 25.3 mg per deciliter], P less than 0.05). One patient in the placebo group in Study 1 died. As compared with those who received placebo, the patients who received dexamethasone became afebrile earlier (1.6 vs. 5.0 days; P less than 0.001) and were less likely to acquire moderate or more severe bilateral sensorineural hearing loss (15.5 vs. 3.3 percent; P less than 0.01). Twelve patients in the two placebo groups (14 percent) had severe or profound bilateral hearing loss requiring the use of a hearing aid, as compared with 1 (1 percent) in the two dexamethasone groups (P less than 0.001). We conclude that dexamethasone is beneficial in the treatment of infants and children with bacterial meningitis, particularly in preventing deafness.

Effect of metabolic products of muscular contraction on discharge of group III and IV afferents

Abstract: Static muscular contraction has been firmly established to reflexly increase cardiovascular and ventilatory function. Although group III and IV fibers with endings in muscle have been shown to comp...

Regulation of the Synthesis of Steroidogenic Enzymes in Adrenal Cortical Cells by ACTH

Abstract: The mechanism of steroid hormone regulation of specific gene expression in target cells has provided a major focus of interest for investigators concerned with molecular mechanisms involved in cell regulation. This work has been given renewed impetus by the recent cloning and characterization of several steroid hormone receptors (1-6), the trans-acting elements which, upon binding specific ligands, namely the steroid hormones, interact with specific regions of many eukaryotic genes to alter their expression. In contrast, there has been considerably less interest in the mechanisms of regulation of steroid hormone biosynthesis. Yet this is also a topic of great importance, not only because these reactions provide the ligands that interact with the steroid hormone receptors, but also because the steroidogenic enzymes provide excellent model systems for studying the regulation of gene expression by cAMP-dependent mechanisms and by mechanisms involving protein kinase C and tyrosine kinase activity. A variety of mechanisms appear to regulate steroid hydroxylase gene expression in a given cell, and tissue-specific as well as developmental factors play important roles also. In this review, we focus primarily on the regulation of steroid hydroxylase gene expression by cAMP­ dependent mechanisms and, in particular, the mechanisms of ACTH regula­ tion of the synthesis of the steroidogenic enzymes present in the adrenal cortex.

Complications in arthroscopic surgery performed by experienced arthroscopists

Abstract: Summary Twenty-one experienced arthroscopists participated in a prospective, 19-month study to analyze complications in arthroscopic surgery of the knee and other joints. Participants responded to a monthly questionnaire that provided information on a case-by-case basis for the duration of the study. A total of 63 specific procedures were studied. A total of 10,262 procedures were recorded. Procedures performed on the knee joint were most prevalent in the study (8,741 or 86%). Complications were placed in one of 11 descriptive categories for analysis; 173 complications occurred and the overall complication rate was 1.68%. The types of complications recorded in order of frequency were hemarthrosis, 60.1%; infection, 12.1%; thromboembolic disease, 6.9%; anesthetic complications, 6.4%; instrument failure, 2.9%; reflex sympathetic dystrophy, 2.3%; ligament injury, 1.2%; and fracture and neurologic injuries, 0.6% each. The remainder were miscellaneous complications, 6.9%. No vascular injuries were reported. The two most frequent procedures reported were medial meniscectomy (2,468) with a complication rate of 1.78%, and lateral meniscectomy (1,149) with a complication rate of 1.48%. Overall, there was a lower incidence of complications in meniscal repair (1.29%), including both inside-out and outside-in techniques, than in meniscectomy (1.69%). In-depth information was gathered on each complication. In addition, profiles on surgical techniques and surgical equipment were obtained from each of the contributing surgeons. The complication rate in arthroscopic surgery was found to be higher than had been previously found in retrospective surveys. With further analysis of the complication data and profiles of the surgeons, protective techniques can be further identified to help reduce the incidence of complications in arthroscopic surgery.

Relationship of Animal Protein-Rich Diet to Kidney Stone Formation and Calcium Metabolism

Abstract: We wished to determine whether different types of dietary protein might have different effects on calcium metabolism and on the propensity for renal stone formation. Fifteen young normal subjects were studied during three 12-day dietary periods during which their diet contained vegetable protein, vegetable and egg protein, or animal protein. While these three diets were constant with respect to Na, K, Ca, P, Mg, and quantity of protein, they had progressively higher sulfur contents. As the fixed acid content of the diets increased, urinary calcium excretion increased from 103 +/- 15 ( +/- SEM) mg/day (2.6 +/- 0.4 mmol/day) on the vegetarian diet to 150 +/- 13 mg/day (3.7 +/- 0.3 mmol/day) on the animal protein diet (P less than 0.02). Despite the increased urinary calcium excretion, there was a modest reduction of urinary cAMP excretion and serum PTH and 1,25-dihydroxyvitamin D levels consistent with acid-induced bone dissolution. There was no change in fractional intestinal 47Ca absorption. The inability to compensate for the animal protein-induced calciuric response may be a risk factor for the development of osteoporosis. The animal protein-rich diet was associated with the highest excretion of undissociated uric acid due to the reduction in urinary pH. Moreover, citrate excretion was reduced because of the acid load. However, oxalate excretion was lower than during the vegetarian diet [26 +/- 1 mg/day (290 +/- 10 mumol/day) vs. 39 +/- 2 mg/day (430 +/- 20 mumol/day); P less than 0.02]. Urinary crystallization studies revealed that the animal protein diet, when its electrolyte composition and quantity of protein were kept the same as for the vegetarian diet, conferred an increased risk for uric acid stones, but, because of opposing factors, not for calcium oxalate or calcium phosphate stones.

Restenosis after successful coronary angioplasty. Pathophysiology and prevention.

Abstract: OVER the past decade, percutaneous transluminal coronary angioplasty has gained wide acceptance as the procedure of choice in many patients with atherosclerotic coronary artery disease. As experience with the procedure has grown, its rate of success has risen to approximately 90 percent and the incidence of acute complications has fallen; as a result, emergency coronary-artery bypass surgery is required in less than 4 percent of patients.1 2 3 Despite these improvements, re-Stenosis in the days, weeks, or months after successful angioplasty of a narrowed coronary artery occurs in 25 to 35 percent of patients,3 4 5 6 7 or 45 to 55 percent of those with . . .

Comparison of a high-carbohydrate diet with a high-monounsaturated-fat diet in patients with non-insulin-dependent diabetes mellitus.

Abstract: We compared a high-carbohydrate diet with a high-fat diet (specifically, a diet high in monounsaturated fatty acids) for effects on glycemic control and plasma lipoproteins in 10 patients with non-insulin-dependent diabetes mellitus (NIDDM) receiving insulin therapy. The patients were randomly assigned to receive first one diet and then the other, each for 28 days, in a metabolic ward. In the high-carbohydrate diet, 25 percent of the energy was in the form of fat and 60 percent in the form of carbohydrates (47 percent of the total energy was in the form of complex carbohydrates); the high-monounsaturated-fat diet was 50 percent fat (33 percent of the total energy in the form of monounsaturated fatty acids) and 35 percent carbohydrates. The two diets had the same amounts of simple carbohydrates and fiber. As compared with the high-carbohydrate diet, the high-monounsaturated-fat diet resulted in lower mean plasma glucose levels and reduced insulin requirements, lower levels of plasma triglycerides and very-low-density lipoprotein cholesterol (lower by 25 and 35 percent, respectively; P less than 0.01), and higher levels of high-density lipoprotein (HDL) cholesterol (higher by 13 percent; P less than 0.005). Levels of total cholesterol and low-density lipoprotein (LDL) cholesterol did not differ significantly in patients on the two diets. These preliminary results suggest that partial replacement of complex carbohydrates with monounsaturated fatty acids in the diets of patients with NIDDM does not increase the level of LDL cholesterol and may improve glycemic control and the levels of plasma triglycerides and HDL cholesterol.

Androgen Abuse by Athletes

Abstract: Introduction ANDROGEN abuse by athletes constitutes only a portion of the problem of androgen misuse by the general population (1) and only a minor aspect of the doping of athletes with drugs presumed to enhance athletic ability (2, 3). Indeed, of the drugs banned by the International Olympic Committee, steroids account only for about 15% (4). This particular form of drug abuse stems from the convergence of several separate misconceptions. The first was the recognition that the administration of androgens to hypogonadal males causes an increase in nitrogen retention and an increase in muscle mass and lean body weight (5). It followed that the differences in muscle mass between men and women are largely due to differences in testosterone levels, and it was assumed that the administration of androgens in supraphysiological amounts to normal men would do even more than the normal amount. The second misconception was that the anabolic (muscle promoting) and androgenic (virilizing) actions of the hormone are e...

A View of Acidic Intracellular Compartments

Abstract: C ONSIDERABLE evidence has accumulated over the past ten years that the interior of both the endocytic and exocytic vacuolar apparatus in cells is maintained at a low pH (30, 47, 60). The interior of endocytic vesicles (4, 17, 29, 57, 59), lysosomes (37, 43), portions of the transGolgi apparatus (3, 38, 39), certain secretory vesicles (14, 22, 23, 38, 48), and plant tonoplasts (7) is acidic. The maintenance of the high H § concentration depends upon the properties of the surrounding membrane and the vectorial movement of protons mediated by an ATP dependent H § pump (1, 30, 47). A variety of different techniques have been used to study the function of low pH compartments. (a) Using purified secretory vesicles (24, 36), yeast vacuoles (49), and lysosomes (42, 53), the influx and effiux of low molecular weight solutes has been shown to depend on both a transmembrane H § gradient and an electrical gradient generated by an ATPdependent H § pump in the membrane of these vesicles. (b) Several laboratories have isolated mutant cell lines that are defective in H § pumping (28, 31, 45); these cells are resistant to certain toxins that gain entry to cells by acidic endosomes and they are unable to obtain iron from transferrin during receptor-mediated endocytosis. (c) Reagents that either neutralize low pH compartments or dissipate H § gradients inhibit a variety of endocytic and exocytic activities including receptor recycling during receptor-mediated endocytosis (9), the sorting of both content and membrane proteins during exocytosis (19, 33, 58) and endocytosis (9), and the posttranslational processing of macromolecules that pass through the Golgi apparatus (39). To better understand the function of acidic compartments, investigators have studied H § gradients in the living cell using vital pH indicators. When taken up by cells, these indicators either selectively accumulate in low pH compartments or detect the pH of the compartment in which they reside. As outlined below, recent advances in immunocytochemistry, flow cytometry, and videoenhanced microscopy offer the interested investigator new opportunities for using these indicators to \"capture\" the H § gradient as it exists in the living cell and detect the chemical reactions that occur in that environment.

Lymphokine-mediated regulation of the proliferative response of clones of T helper 1 and T helper 2 cells.

Abstract: Murine Th1 and Th2 subsets differ not only in the lymphokines they produce, but also functionally. It is not clear what factors influence the preferential activation of one subset versus the other and what regulatory interactions exist between them. The purpose of this study was to examine the effect of lymphokines produced by clones of Th1 cells (IL-2 and IFN-gamma), Th2 cells (IL-4), and APC (IL-1) on the proliferative response of Th1 and Th2 cells after antigenic stimulation. Activation of both types of clones in the presence of antigen and APC resulted in the acquisition of responsiveness to the proliferative effects of both IL-2 and IL-4, although Th2 cells were more responsive to IL-4 than Th1 cells. Responsiveness of Th1 and Th2 cells to both lymphokines decreased with time after initial antigenic activation; Th1 cells lost their responsiveness to IL-4 more rapidly and to IL-2 more slowly than Th2 cells. IFN-gamma partially inhibited the IL-2 and IL-4-mediated proliferation of Th2, but not Th1 cells. Although the presence of IL-1 was not required for the response of Th1 or Th2 cells to IL-4, its presence resulted in a synergistic effect with IL-2 or IL-4 in Th2 but not in Th1 cells. Both subsets responded to a mixture of IL-2 and IL-4 in synergistic fashion. Delayed addition and wash-out experiments indicated that both IL-2 and IL-4 had to be present simultaneously in order for synergy to occur. These results suggest that Th cell subsets might regulate each other via the lymphokines that they secrete and that the pathways of IL-2 and IL-4 mediated proliferation are interrelated.

Abnormal I-123 metaiodobenzylguanidine myocardial washout and distribution may reflect myocardial adrenergic derangement in patients with congestive cardiomyopathy.

Abstract: I-123 metaiodobenzylguanidine (MIBG) is a new radiopharmaceutical with properties that allow the characterization of the sympathetic innervation of several organ systems. In this study, we used MIBG with tomographic imaging to evaluate noninvasively the differences in myocardial sympathetic innervation in 14 healthy volunteers and 16 patients with severe dilated cardiomyopathy (CM). Initial (15-minute) images demonstrated no significant differences in MIBG concentration in the hearts of patients with CM and of healthy volunteers. However, the myocardial retention of MIBG was significantly reduced in the patients with CM. Expressed as the percent washout from 15 to 85 minutes, the patients with CM had a 28 +/- 12% washout rate compared with 6 +/- 8% in the controls (p less than 0.001). A small subset of patients from each group imaged at 4-hour intervals demonstrated even greater disparity in washout rates. In addition, the patients with CM had significantly greater heterogeneity in the MIBG activity distribution within the myocardial images. There was 47 +/- 15% intraimage variability in MIBG distribution in the patients with CM and 22 +/- 9% variation in the controls (p less than 0.001). We conclude from these data that the myocardial distribution and kinetics of MIBG in images obtained from patients with CM differ significantly from those of controls and that the MIBG patterns may be used as a relatively noninvasive means to evaluate the severity of altered adrenergic innervation in the hearts of these patients.

Mitochondrial transformation in yeast by bombardment with microprojectiles

Abstract: The genetic transformation of mitochondria and chloroplasts has been an intractable problem. The newly developed "biolistic" (biological ballistic) process was used to deliver DNA into yeast cells to stably transform their mitochondria. A nonreverting strain, which is respiratory deficient because of a deletion in the mitochondrial oxi3 gene, was bombarded with tungsten microprojectiles coated with DNA bearing sequences that could correct the oxi3 deletion. Respiratory-competent transformants were obtained in which the introduced oxi3 DNA is integrated at the homologous site in the mitochondrial genome. Organelle genomes can now be manipulated by molecular genetic techniques in the same way as nuclear genomes.

Acute effects of exercise on MR imaging of skeletal muscle in normal volunteers

Abstract: Exercise is known to produce changes in the amount and distribution of water in skeletal muscle. Because MR imaging is highly sensitive to changes in water distribution, these changes should be detectable under appropriate imaging conditions. Imaging of the forearms and/or legs was performed in 16 volunteers at 0.35 T, before and after exercise. Exercises included finger flexion and extension, wrist flexion, ankle plantar flexion, and great toe extension. In the case of handgrip exercise, the level of exertion was quantitated. Individual muscles were frequently indistinguishable on preexercise scans. After exercise, active and inactive muscles could be clearly distinguished. For example, in the flexor digitorum profundus, finger flexion resulted in an increase in the image-derived estimate of T1 (T1 postexercise was 1037 +/- 162 msec vs T1 preexercise of 590 +/- 49 msec, p less than .001). T2 also increased (T2 postexercise was 35 +/- 2 msec vs T2 preexercise of 28 +/- 1 msec, p less than .001). Relative spin density also increased (p less than .001). T1, T2, and spin density subsequently decreased with time but were still increased above baseline at 10 min postexercise (p less than .005). Signal changes correlated moderately with the level of exertion (r = .63) and fatigue (r = .45). Vascular occlusion did not prevent intensity changes. Thus, changes in skeletal muscle MR signal intensity occur with exercise and appear to parallel known alterations in water distribution.

Isolation of a full-length cDNA insert encoding human aromatase system cytochrome P-450 and its expression in nonsteroidogenic cells

Abstract: The isolation and cloning of a full-length cDNA insert complementary to mRNA encoding human aromatase system cytochrome P-450 is reported. The insert contains an open reading frame encoding a protein of 503 amino acids. This gene is clearly a member of the cytochrome P-450 gene superfamily, because the sequence contains regions of marked homology to those of other members, notably a putative membrane-spanning region, I helix, Ozols, and heme-binding regions. The cDNA was inserted into a modified pCMV vector and expressed in COS-1 monkey kidney tumor cells. The expressed protein was similar in size to human placental aromatase system cytochrome P-450, as detected by immunoblot analysis, and catalyzed the aromatization of androstenedione, testosterone, and 16 alpha-hydroxyandrostenedione. This activity was inhibited by the known aromatase inhibitors, 4-hydroxyandrostenedione and econazole. Thus the several steps involved in the aromatization reaction appear to be catalyzed by a single polypeptide chain, which can metabolize the three major physiological substrates.

Structural changes in glycogen phosphorylase induced by phosphorylation.

Abstract: A comparison of the refined crystal structures of dimeric glycogen phosphorylase b and a reveals structural changes that represent the first step in the activation of the enzyme. On phosphorylation of serine-14, the N-terminus of each subunit assumes an ordered helical conformation and binds to the surface of the dimer. The consequent structural changes at the N- and C-terminal regions lead to strengthened interactions between subunits and alter the binding sites for allosteric effectors and substrates.

Bilaterality in anterior cruciate ligament injuries Associated intercondylar notch stenosis

Abstract: Nonsimultaneous, bilateral ACL injuries are not uncommon. We studied a group of patients with these injuries to determine possible predisposing factors that could aid in early detection and prevention of contralateral ACL injury. Retrospective analysis of 1,120 patients with ACL ruptures who were treated between 1983 and 1987 revealed 45 patients with bilateral ruptures. Complete follow-up data were available for 41 of these patients. We examined age at initial injury, sex, interval between initial and contralateral ACL injury, mechanism of injury, activity at injury, medical and family histories, treatment of initial injury, and radiographic measurement of intercondylar notch width. The overall incidence of bilaterality was 4.01% in the 28 male and 13 female patients. Their average age was 19 years and 10 months. The average interval between initial and contralateral injury was 47 months. A noncontact cutting maneuver was the most common mechanism of injury. We devised a method to measure and compare intercondylar notch widths on plain radiographs. We compared the mean notch width index (NWI) of the bilateral group to the mean NWI of a group of 50 consecutive patients with "normal" knees and to the mean NWI of 50 consecutive patients with acute ACL ruptures. The mean NWI for the normal group was .2338, for the acute ACL group, .2248, and for the bilateral group, .1961. We noted a statistically significant difference when we compared the bilateral group to the normal and acute groups (P less than 0.0001, respectively). There was no statistically significant difference between the NWI of the normal and acute ACL groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Native structure and physical properties of bovine brain kinesin and identification of the ATP-binding subunit polypeptide.

Abstract: Kinesin was extensively purified from bovine brain cytosol by a microtubule-binding step in the presence of 5'-adenylyl imidodiphosphate (AMP-PNP), followed by gel filtration chromatography and sucrose gradient ultracentrifugation. The products consistently contained 124,000 (124K) and 64,000 (64K) dalton polypeptides. These two polypeptides appear to represent heavy and light chains of kinesin, respectively, because they copurified on sucrose gradients to a constant and equimolar stoichiometry and bound stably to microtubules in the presence of AMP-PNP but not ATP. The mobilities of 124K and 64K in sodium dodecyl sulfate-polyacrylamide gels under reducing conditions were the same as under nonreducing conditions. A diffusion coefficient of (2.24 +/- 0.21) X 10(-7) cm2 s-1 and a sedimentation coefficient of (9.56 +/- 0.34) X 10(-13) s were determined for native kinesin by gel filtration and sucrose gradient ultracentrifugation, respectively. These values were used to calculate a native molecular weight of about 379,000 and suggest that kinesin has an axial ratio of approximately 20. Extensively purified kinesin exhibited microtubule-activated ATPase activity, and only the 124K subunit incorporated ATP in photoaffinity labeling experiments using [32P]ATP. Collectively, these data favor the interpretation that bovine brain kinesin is a highly elongated, microtubule-activated ATPase comprising two subunits each of 124,000 and 64,000 daltons, that the subunits are not linked to one another by disulfide bonds, and that the heavy chains are the ATP-binding subunits.