Demonstration of dose-dependent global and regional cocaine-induced reductions in brain blood flow using a novel approach to quantitative single photon emission computerized tomography

Ischemic stroke is a common cause of morbidity and mortality in cocaine addicts. Because the previous semiquantitative single photon emission computerized tomography (SPECT) method for measuring brain blood flow does not quantify blood flow, the magnitude and specificity of cocaine's effects during drug taking has not been well established. Here, using a novel quantitative approach to SPECT, we established that intravenous cocaine administration to nine recently abstinent cocaine-dependent subjects was associated with significant decreases in global and regional brain blood flow to dopamine-rich areas such as the prefrontal, frontal temporal, and subcortical gray matter. Establishing the utility of this relatively new quantitative SPECT technique provides an important tool for the management of vascular disorders of the brain. Additionally, identifying the site-specific effects of cocaine provides targets for the development of putative therapeutic medications to attenuate or minimize ischemic stroke in cocaine addicts.

Isradipine prevents global and regional cocaine-induced changes in brain blood flow: a preliminary study

The L-type calcium channel antagonist, isradipine, reduces brain ischemia in animal models of ischemic stroke. These effects of isradipine appear more pronounced in dopamine (DA) rich brain regions. These same DA-rich brain regions have also been shown to be the areas most affected by cocaine-induced ischemic changes. Using a novel quantified approach to single photon emission computerized tomography, we demonstrated that isradipine pre-treatment prevented cocaine-induced ischemic changes, especially in these DA-rich brain regions. This is the first demonstration that any medication, including isradipine, can prevent the ischemic effects of cocaine on brain blood flow. Isradipine may, therefore, be a useful therapeutic agent for the prevention of brain ischemia in cocaine addicts.

Effects of acute intravenous cocaine on cardiovascular function, human learning, and performance in cocaine addicts

Continuous non-invasive cardiovascular monitoring in eight healthy cocaine addicts receiving intravenous cocaine (0.325 mg/kg or 0.650 mg/kg) or placebo in double-blind, randomized, cross-over fashion demonstrated significant dose-dependent increases in pulse and mean arterial pressure following cocaine. Pulse and mean arterial pressure peaked 5 min post-cocaine injection and maximal response was sustained for a further 15 min and 35 min afterwards, respectively. Cocaine administration had no significant effect on peripheral oxygen saturation, and no clinically significant abnormalities of rhythm or conduction were seen on the electrocardiogram. These doses and method of single-dose intravenous cocaine administration, and our procedures for cardiovascular monitoring, appear relatively safe for laboratory studies of healthy cocaine addicts with no pre-existing cardiovascular disease. In addition, cocaine-taking (0.325 mg/kg i.v. and 0.650 mg/kg i.v.) was associated with enhanced attention (i.e. increased numbers of correct responses on the Rapid Visual Information Processing Task), but the trend towards reduced reaction time did not achieve statistical significance. Cocaine-taking resulted in a small but statistically insignificant improvement in learning on the Digit Symbol Substitution Task. These results suggest that cocaine-taking in rested subjects is associated with some cognitive enhancement.

Biochemical characterization of the S135L allele of galactose-1-phosphate uridylyltransferase associated with galactosaemia

Impairment of the human enzyme galactose-1-phosphate uridylyltransferase (GALT) results in the potentially lethal disorder galactosaemia. The S135L mutation, which accounts for almost 50% of the GALT alleles in galactosaemia patients of African-American descent, has been associated with activities ranging from null to wild-type by different investigators examining cell lysates representing different tissues or model systems. Because of the crude nature of the lysates examined, however, and the absence of quantitative measures concerning GALT abundance in most of those lysates, the available data do not distinguish between differences in GALT enzyme expression/abundance, specific activity, or kinetic constants in these different tissues or systems. In an effort to overcome this uncertainty and investigate the biochemical impact of the S135L substitution on human GALT function under defined conditions, we have overexpressed both wild-type and S135L-mutant GALT sequences in a null-background yeast expression system, and purified both proteins to near homogeneity. Abundance of the wild-type and mutant proteins in crude yeast lysates differed by approximately 2-fold. Kinetic studies of the purified proteins, however, demonstrated that although K(m) values differed by < 2-fold, specific activities differed by 10-fold. Temperature-activity profiles revealed no significant differences, and coprecipitation studies demonstrated that S135L-hGALT subunits remained competent to self-associate in vivo. We conclude that the S135L substitution causes either steric or electrochemical changes sufficiently close to the active site in human GALT to result in partial impairment of the transferase reaction.

Functional requirements of the active site position 185 in the human enzyme galactose-1-phosphate uridylyltransferase

The active site of galactose-1-phosphate uridylyltransferase (GALT) includes a HPH sequence that has been conserved in all species examined from Escherichia coli to humans. The crystal structure of the E. coli enzyme suggests that this proline is important in positioning the active site histidine (His-166) near the substrate. To examine the role of this proline in the homologous human sequence, we have performed saturating mutagenesis at Pro-185 within human GALT and characterized each resultant mutant enzyme using a yeast expression system. Activity analyses in crude lysates indicated that only proline at position 185 produced wild-type levels of activity, although five other amino acids, Ala, Gly, Ser, Gln, and Glu, all produced partially active enzymes. Western blot analyses of the GALT proteins in these lysates demonstrated that abundance varied from 9-118% of wild-type and was independent of activity. All five active mutant proteins were purified and characterized with regard to specific activity, apparent Km for both substrates, and temperature-dependence of activity. Finally, modeling of these mutations onto the conserved E. coli active site structure was performed. Together, these results provide functional evidence demonstrating the critical role of Pro-185 in facilitating the transferase reaction.

Myosin heavy chain isoforms regulate muscle function but not myofibril assembly

Myosin heavy chain (MHC) is the motor protein of muscle thick filaments. Most organisms produce many muscle MHC isoforms with temporally and spatially regulated expression patterns. This suggests that isoforms of MHC have different characteristics necessary for defining specific muscle properties. The single Drosophila muscle Mhc gene yields various isoforms as a result of alternative RNA splicing. To determine whether this multiplicity of MHC isoforms is critical to myofibril assembly and function, we introduced a gene encoding only an embryonic MHC into Drosophila melanogaster. The embryonic transgene acts in a dominant antimorphic manner to disrupt flight muscle function. The transgene was genetically crossed into an MHC null background. Unexpectedly, transformed flies expressing only the embryonic isoform are viable. Adult muscles containing embryonic MHC assemble normally, indicating that the isoform of MHC does not determine the dramatic ultrastructural variation among different muscle types. However, transformed flies are flightless and show reduced jumping and mating ability. Their indirect flight muscle myofibrils progressively deteriorate. Our data show that the proper MHC isoform is critical for specialized muscle function and myofibril stability.

Heterodimer formation and activity in the human enzyme galactose-1-phosphate uridylyltransferase

One of the fundamental questions concerning expression and function of dimeric enzymes involves the impact of naturally occurring mutations on subunit assembly and heterodimer activity. This question is of particular interest for the human enzyme galactose-l-phosphate uridylyl-transferase (GALT), impairment of which results in the inherited metabolic disorder galactosemia, because many if not most patients studied to date are compound heterozygotes rather than true molecular homozygotes. Furthermore, the broad range of phenotypic severity observed in these patients raises the possibility that allelic combination, not just allelic constitution, may play some role in determining outcome. In the work described herein, we have selected two distinct naturally occurring null mutations of GALT, Q188R and R333W, and asked the questions (i) what are the impacts of these mutations on subunit assembly, and (ii) if heterodimers do form, are they active? To answer these questions, we have established a yeast system for the coexpression of epitope-tagged alleles of human GALT and investigated both the extent of specific GALT subunit interactions and the activity of defined heterodimer pools. We have found that both homodimers and heterodimers do form involving each of the mutant subunits tested and that both heterodimer pools retain substantial enzymatic activity. These results are significant not only in terms of their implications for furthering our understanding of galactosemia and GALT holoenzyme structure-function relationships but also because the system described may serve as a model for similar studies of other complexes composed of multiple subunits.

Common lower extremity problems in children

This article discusses the diagnosis and management of common lower extremity problems in children, including flatfeet, torsional and angular problems, developmental dislocation of the hip, and slipped capital femoral epiphysis. These problems represent some of the more common lower extremity conditions found in children from infancy to adolescence.

A memorial service for families of children who died from cancer and blood disorders

The grief of staff who work with dying children and the grief of family members after the death of a child has been widely documented. Interventions to facilitate grieving have been extensively developed for parents but less so for siblings and staff. This article describes one approach, a memorial service, for families and staff that has wide applicability for providing support after a death. The memorial service provides families and staff with a healing ritual of remembrance, a source of closure after the death, and a recognition of the relationships established between families and staff. The service particularly legitimizes the staff's grief experience. The organization, implementation, and evaluation of such a program is discussed.

Relation of systemic and local muscle exercise capacity to skeletal muscle characteristics in men with congestive heart failure

OBJECTIVES

The present study was undertaken to further characterize changes in skeletal muscle morphology and histochemistry in congestive heart failure and to determine the relation of these changes to abnormalities of systemic and local muscle exercise capacity.

BACKGROUND

Abnormalities of skeletal muscle appear to play a role in the limitation of exercise capacity in congestive heart failure, but information on the changes in muscle morphology and biochemistry and their relation to alterations in muscle function is limited.

METHODS

Eighteen men with predominantly mild to moderate congestive heart failure (mean +/- SEM New York Heart Association functional class 2.6 +/- 0.2, ejection fraction 24 +/- 2%) and eight age- and gender-matched sedentary control subjects underwent measurements of peak systemic oxygen consumption (VO2) during cycle ergometry, resistance to fatigue of the quadriceps femoris muscle group and biopsy of the vastus lateralis muscle.

RESULTS

Peak VO2 and resistance to fatigue were lower in the patients with heart failure than in control subjects (15.7 +/- 1.2 vs. 25.1 +/- 1.5 ml/min-kg and 63 +/- 2% vs. 85 +/- 3%, respectively, both p < 0.001). Patients had a lower proportion of slow twitch, type I fibers than did control subjects (36 +/- 3% vs. 46 +/- 5%, p = 0.048) and a higher proportion of fast twitch, type IIab fibers (18 +/- 3% vs. 7 +/- 2%, p = 0.004). Fiber cross-sectional area was smaller, and single-fiber succinate dehydrogenase activity, a mitochondrial oxidative marker, was lower in patients (both p < or = 0.034). Likewise, the ratio of average fast twitch to slow twitch fiber cross-sectional area was lower in patients (0.780 +/- 0.06 vs. 1.05 +/- 0.08, p = 0.019). Peak VO2 was strongly related to integrated succinate dehydrogenase activity in patients (r = 0.896, p = 0.001). Peak VO2, resistance to fatigue and strength also correlated significantly with several measures of fiber size, especially of fast twitch fibers, in patients. None of the skeletal muscle characteristics examined correlated with exercise capacity in control subjects.

CONCLUSIONS

These results indicate that congestive heart failure is associated with changes in the characteristics of skeletal muscle and local as well as systemic exercise performance. There are fewer slow twitch fibers, smaller fast twitch fibers and lower succinate dehydrogenase activity. The latter finding suggests that mitochondrial content of muscle is reduced in heart failure and that impaired aerobic-oxidative capacity may play a role in the limitation of systemic exercise capacity.

Characterization of the N314D allele of human galactose-1-phosphate uridylyltransferase using a yeast expression system

Transferase-deficiency galactosemia is an inborn error of metabolism resulting from impairment of the enzyme galactose-1-phosphate uridylyltransferase (GALT), which normally catalyzes the second step of the Leloir pathway of galactose metabolism. Several recent studies have linked a previously reported substitution, N314D (asn to asp at position 314), with both the Duarte and Los Angeles (LA) variant alleles of GALT. While both variants demonstrate similar mobility shifts relative to the normal enzyme on isoelectric focusing (IEF) gels, one (Duarte) is associated with diminished activity, while the other (LA) is associated with greater than normal activity. Therefore, although the concordance rates between N314D and both of these phenotypes are compelling, the question remains as to whether N314D alone is sufficient to cause either or both variants. To address the question of precisely what properties of variant GALT can be attributed to the N314D substitution alone, we have modeled both the wildtype and N314D-GALT alleles in a previously defined yeast expression system, and characterized each with respect to activity, abundance, subunit interaction, and mobility on isoelectric focusing gels. Our results indicate that the N314D subunit dimerizes well both with wildtype GALT and with itself and that the N314D substitution is sufficient to confer the expected shift of IEF banding pattern associated with both the Duarte and LA variant proteins isolated from human cells. However, our results also suggest that N314D-GALT retains full specific activity, thereby calling into question the suggestion that N314D encodes the Duarte variant of GALT.

Insulin-like growth factor 1 and functional status in healthy older men

OBJECTIVE

To determine if insulin-like growth factor 1 (IGF-1) is associated with strength and functional ability in healthy older men.

DESIGN

Cross-sectional study.

SETTING

San Francisco Department of Veterans Affairs Medical Center.

PARTICIPANTS

One hundred four ambulatory community-dwelling men.

MEASUREMENTS

Serum IGF-1 levels were obtained. Measured variables included strength of the knee flexors and extensors, handgrip, score on the Physical Performance Test, body composition, and three tests of cognitive function.

RESULTS

The subjects' mean age was 75.5 +/- 4.9 (SD) years (range 70-94 years), and their mean IGF-1 level was 134.7 +/- 43.6 ng/mL. The univariate association of age with the variables was much stronger than the univariate association of IGF-1 with the same variables. In multivariable models, age, but not IGF-1, was associated with the variables.

CONCLUSION

In this study of healthy older men, age is the most important variable in predicting functional decline. There was no association of IGF-1 levels to functional status independent of age.

Relation of the nine-minute self-powered treadmill test to maximal exercise capacity and skeletal muscle function in patients with congestive heart failure

The 9-minute self-powered treadmill test has been employed to evaluate submaximal exercise capacity in heart failure patients, but its relation to maximal exercise capacity and to indexes of skeletal muscle function has not been well defined. Two protocols were utilized. The first evaluated the relation of the peak oxygen uptake (VO2) achieved on the self-powered treadmill to that during a symptom-limited treadmill protocol, and examined the reproducibility of this test. Thirteen patients (aged 62 +/- 2 years, in New York Heart Association class I to III [2.3 +/- 0.1], ejection fraction 23 +/- 2% [means +/- SEM]) and 10 age-matched sedentary controls were studied. The second protocol, which involved 18 patients (aged 65 +/- 2 years, in New York Heart Association class I to IV [2.4 +/- 0.1], ejection fraction 23 +/- 2%) and 10 age-matched controls evaluated the relation of performance on the self-powered treadmill to maximal systemic exercise capacity on a cycle ergometer and to indexes of skeletal muscle function. In the first protocol, the test was found to be highly reproducible. The proportion of self-powered treadmill to maximal treadmill peak VO2 did not differ significantly between patients and controls (95 +/- 5% vs 87 +/- 6%). In the second protocol, patients achieved a lower peak VO2 (15.6 +/- 1.1 vs 25.6 +/- 0.9 ml/kg/min, p < 0.001), walked a shorter distance on the self-powered treadmill (367 +/- 32 vs 667 +/- 28 m, p < 0.001), and exhibited less knee extensor work capacity (1,075 +/- 116 vs 1,390 +/- 110 ft-lbs, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise intolerance in chronic heart failure is not associated with impaired recovery of muscle function or submaximal exercise performance

OBJECTIVES

This study investigated whether recovery of skeletal muscle function is impaired in patients with heart failure and whether impaired recovery is associated with abnormal submaximal systemic exercise tolerance during repeated testing.

BACKGROUND

Patients with heart failure experience fatigue during daily activities. Because abnormalities of skeletal muscle play a role in their exercise intolerance, these symptoms may reflect a delay in muscle recovery and a resulting limitation in submaximal exercise tolerance.

METHODS

Two protocols were used. In protocol 1, knee extensor strength and endurance, and their recovery after fatiguing exercise, were evaluated in 11 patients (mean [+/- SEM] age 62 +/- 5 years, New York Heart Association functional class 2.3 +/- 0.2, ejection fraction 24 +/- 5%) and in 10 age-matched sedentary control subjects. Protocol 2 examined the recovery of knee extensor endurance and submaximal exercise tolerance, as quantified on a self-powered treadmill, over 24 h in 18 patients (mean age 65 +/- 3 years, functional class 2.4 +/- 0.2, ejection fraction 23 +/- 3%) and in 10 control subjects.

RESULTS

Peak oxygen consumption was reduced in both heart failure groups (15.4 +/- 1.4 and 15.6 +/- 1.0 ml/kg per min) compared with that in the respective control groups (23.1 +/- 2.9 and 25.6 +/- 1.0 ml/kg per min, both p < 0.05), as was muscle endurance but not muscle strength. In protocol 1, knee extensor endurance recovered more slowly in the patients than in control subjects (to 62 +/- 4% and 87 +/- 7% of the baseline value after 5 min, respectively, p < 0.05). In protocol 2, submaximal exercise tolerance was lower in the patients with heart failure than in control subjects (1,075 +/- 116 vs. 1,390 +/- 110 m), but knee extensor endurance and walking distance recovered fully by 10 and 30 min, respectively.

CONCLUSIONS

Although these findings confirm earlier studies that demonstrated impaired muscle endurance in patients with heart failure, the results provide no evidence that recovery of either muscle function or submaximal exercise tolerance is delayed beyond the initial 5 to 10 min after exercise.

Corticosteroid-binding globulin in preterm infants in an intensive care unit

Blood concentration of corticosteroid-binding globulin (CBG) was measured in 85 preterm (24-36 weeks of gestational age) infants over the first 6 weeks of postnatal life. CBG concentrations directly correlated to gestational age and postnatal age in the first week of life. There was a significant increase in CBG values over the first 6 weeks such that mean values at weeks 4 through 6 were significantly greater than values at weeks 1 and 2. Postnatal CBG values were significantly lower in infants who had pulmonary disease during week 1 (p = 0.001). In summary, CBG values were directly correlated to gestational and postnatal age, and negatively correlated to acute illness. We speculate that the lower CBG values with lung disease may reflect an ongoing inflammatory response.

At the front line of care. The importance of nutrition in wound management

While the importance of nutrition in wound healing has been acknowledged, nutritional assessment is often overlooked. It is therefore vital that patients' nutritional status are assessed on an ongoing basis.

Influence of Planter Type and Seeding Rate on Yield and Disease Incidence in Peanut1

Variability of peanut (Arachis hypogaea L.) seedling spacing, and yield were compared for a conventional and a vacuum-type planter in field studies conducted in 1991 and 1992. Vacuum-type planters have an improved seed metering system and are considered to be more precise. This added precision may serve to compensate for lower than normal seeding rates. Seeding rates evaluated decreased in a step-wise manner from the normal range of 123 to 101 kg/ha, to a minimum of 34 kg/ha. Spacing between individual seedlings was measured after emergence. The occurrence of tomato spotted wilt (TSWV) and southern stem rot were also determined. In 1991 and across all seeding rates, variability in seedling spacing (i.e. standard deviation) was identical between the two planters. In 1992, at 3 of the five seeding rates (34,56, and 101 kg/ha) standard deviation was less with the vacuum planter. In both years yield and disease occurrence was influenced only by seeding rate, and was independent of planter type. TSWV was inversely related to seeding rate, the opposite relationship occurred with southern stem rot. Maximum yield was achieved with a seeding rate of 101 kg/ha.

Skeletal muscle size: relationship to muscle function in heart failure

Abnormalities of skeletal muscle function and metabolism are common in patients with congestive heart failure (CHF) and appear to contribute to systemic exercise limitation. Although the mechanism for these differences is unclear, one possibility is skeletal muscle atrophy. In 21 CHF patients and 12 sex- and age-matched sedentary control subjects, we quantified muscle size as maximal cross-sectional area (MCSA) of thigh muscles measured by magnetic resonance imaging and determined the relationship between muscle size and muscle function. Muscle strength was measured as maximum force developed during isometric contractions, and muscle endurance was quantified as the decline in force during 15 consecutive isokinetic knee extensions (measured as ratio of mean peak torque of last 3 and first 3 extensions). MCSAs of thigh muscles (141 +/- 28 vs. 167 +/- 47 cm2, P < 0.05) and knee extensors (62 +/- 13 vs. 75 +/- 13 cm2; P < 0.05) were both significantly smaller in patients than in control subjects. These differences persisted after normalization for body size. Isometric strength was less, but not significantly so, in patients (126 +/- 39 vs. 135 +/- 43 Nm; P = NS), but muscle endurance was markedly impaired (endurance ratio 0.67 +/- 0.14 vs. 0.83 +/- 0.11; P < 0.05). A strong correlation was found between isometric strength (r = 0.76) and MCSA of knee extensors, but only a weak correlation between dynamic endurance and MCSA was seen. We conclude that muscle size is smaller in CHF patients but that maximal force generated per area of muscle is not impaired.(ABSTRACT TRUNCATED AT 250 WORDS)

A clinical therapeutic trial of cyclosporine in myasthenia gravis

We randomly assigned 39 patients with steroid-dependent generalized myasthenia gravis to treatment with cyclosporine (5 mg/kg per body weight in divided doses) or placebo. Duration of treatment was 6 months. Patients were evaluated monthly. Primary measures of efficacy were quantified strength testing, antihuman acetylcholine receptor antibody titer, and dosage of corticosteroid medication. At the end of the study, patients in the cyclosporine group had significantly greater improvement in strength (p = 0.004) and a reduction in antireceptor antibody titer (p = 0.01). Percentage reduction of steroid medication was greater in the cyclosporine group, although the difference was not statistically significant (p = 0.12). There were no treatment failures, and there was one drug failure in the cyclosporine group. In the placebo group, there were three treatment failures. No significant nephrotoxicity was noted at this dosage during the first 6 months. During the subsequent 18 months of open-label therapy, continued reduction in steroid dosage occurred. Cumulative side effects, however, caused 35% of patients to discontinue the medication; 10% did so secondary to slowly progressive nephrotoxicity.

High-risk indicators for family involvement in social work in health care: a review of the literature

Shifts in health concerns, fiscal restraints, technological advances, and demands for accountability have created severe tensions within health care settings. New demands point to the need for a redefinition of services. High-risk screening appears to be a clear method of delineating service need. A review of the empirical literature highlights individual, family, and illness variables that alone and together may improve identification of patients and families in need of social work services. The development of screening mechanisms may be a useful vehicle for improved psychosocial care and for the planning of social work services.

Synthetic peptides of human lysosomal cathepsin G with potent antipseudomonal activity

Enzymatically active and inactive (diisopropylfluorophosphate-treated) cathepsin G exerted antibacterial action in vitro against Staphylococcus aureus, whereas only enzymatically active cathepsin G displayed bactericidal action against Pseudomonas aeruginosa. In order to further test the requirement for protease activity for the antipseudomonal action of cathepsin G, synthetic peptides spanning the full-length mature protein were prepared and examined for antibacterial action. Surprisingly, three structurally distinct peptides that correspond to residues 61 to 80, 117 to 136, and 198 to 223 within the full-length protein were found to exert potent antipseudomonal action (> 4.5 logs of killing at 500 micrograms/ml) against P. aeruginosa ATCC 27853 and four mucoid clinical isolates. Only the peptide (CG117-136) corresponding to residues 117 to 136 (117-RPGTLCTVAGWGRVSMRRGT-136) within cathepsin G exerted antibacterial action against the gram-positive pathogen S. aureus. The antipseudomonal action of CG117-136 was rapid and could be inhibited either by increasing concentrations of NaCl or by 0.5 mM MgCl2 plus 0.5 mM CaCl2, and these conditions appeared to reduce binding of the peptide to whole bacteria. Variants of peptide CG117-136 lacking either a hydrophobic N-terminal domain or a positively charged C-terminal domain were found to have significantly less antipseudomonal action than CG117-136. The antibacterial capacity of the all-D-enantiomeric form of peptide CG117-136 was found to be identical to that of the all-L-peptide, suggesting that the mechanism of killing does not require the recognition of a target site possessing a chiral center.

Crop Rotation Studies with Velvetbean (Mucuna deeringiana) for the Management of Meloidogyne spp

Results from a greenhouse experiment at Cabrils, Spain, with two velvetbean (Mucuna deeringiana) accessions (Florida and Mozambique) growing in sterilized sandy loam and inoculated with Meloidogyne arenaria race 2, M. incognita race 1, and M. javanica revealed that the legume was not a host for these nematodes. In contrast, roots of 'Clemson Spineless' okra (Hibiscus esculentum), 'Summer Crookneck' squash (Cucurbita pepo), and 'Davis' soybean (Glycine max) were galled by all three root-knot nematodes. Greenhouse experiments at Auburn, Alabama, using soils infested with Heterodera glycines (race 14) + M. incognita or with H. glycines + M. arenaria (race 2) showed that, in contrast to Davis soybean, a Mexican and the Florida velvetbean accessions were not hosts for the nematodes. An experiment with 'Florunner' peanut (Arachis hypogaea) and the Florida velvetbean in a field infested with M. arenaria (race 1), near Headland, Alabama, showed that significant juvenile populations of the nematode at peanut harvest time were present only in plots with peanut. A microplot rotation experiment demonstrated that 'Black Beauty' eggplant (Solanum melongena) following the Florida velvetbean had heavier shoots and lower numbers of M. arenaria juveniles in the roots and in the soil than eggplant after Summer Crookneck squash or Davis soybean.

Neurophysiological assessment of skeletal muscle fatigue in patients with congestive heart failure

BACKGROUND

Recent research has demonstrated that patients with congestive heart failure (CHF) exhibit significant functional impairment of skeletal muscle and that these changes may be important determinants of exercise capacity. Although muscle strength may be mildly reduced, the most significant abnormality is markedly enhanced muscle fatigue. The goal of the present study is to determine whether accelerated fatigue is caused by impaired muscle activation, as a result of inadequate central motor drive or neuromuscular transmission, or by a change in the muscle itself.

METHODS AND RESULTS

The study population consisted of nine patients with New York Heart Association class I-III CHF and eight sedentary, age- and sex-matched control subjects. Maximal voluntary contraction force of the foot dorsiflexors (primarily the tibialis anterior) was quantified as a measure of muscle strength, isometric endurance was quantified by the time required for force to decline to 60% of maximal during a sustained maximal contraction, and dynamic endurance was defined as the number of maximal contractions required for force to decline to 60% of maximal under a protocol of six repetitions per minute with an incremental duty cycle. The degree of central motor drive failure was quantified by the degree of force augmentation produced by a superimposed tetanic stimulus delivered to the peroneal nerve during the initial maximal voluntary contraction and at the time when force during the sustained isometric contraction declined to 60% of maximal. Neuromuscular junction transmission was examined by quantifying the amplitude of the compound muscle action potential (M wave) in response to a single nerve stimulus during fatiguing exercise. Muscle strength was relatively preserved in the CHF patients versus the control subjects (93 +/- 41 versus 105 +/- 34 lb; p = NS), but isometric endurance (time to decline to 60%, 34 +/- 15 versus 54 +/- 19 seconds; p less than 0.02) and dynamic endurance (number of repetitions before decline to 60%, 30 +/- 6 versus 43 +/- 7 contractions; p less than 0.001) were both impaired. Tetanic nerve stimulation increased force by similar degrees in the two groups, and the amplitude of the M wave did not decline in either group during exercise.

CONCLUSIONS

These findings indicate that enhanced muscle fatigue in patients with CHF is not caused by impaired central motor drive or an abnormality of neuromuscular junction transmission but rather by an abnormality in the muscle itself.

Impaired skeletal muscle function in patients with congestive heart failure. Relationship to systemic exercise performance

In patients with congestive heart failure (CHF), the poor relationship between systemic exercise performance and cardiac function, together with morphologic and metabolic abnormalities in skeletal muscle, raises the possibility that skeletal muscle function may be impaired and limit systemic exercise performance. We assessed strength and endurance of the knee extensors during static and dynamic exercise in 16 patients with Class I-IV CHF and eight age-matched sedentary controls and related these measurements to systemic exercise performance. To assess skeletal muscle function independent of peripheral blood flow, endurance was repeated under ischemic conditions. Strength was not significantly different in the two groups. Dynamic endurance, quantified as the decline in peak torque during 15 successive isokinetic knee extensions, was significantly reduced in the patients compared to controls during aerobic (peak torque 65 vs. 86% of initial for exercise at 90 deg/s and 60 vs. 85% for exercise at 180 deg/s; P less than 0.002 for both), and during ischemic exercise (56 vs. 76% of initial torque; P less than 0.01). Static endurance, defined as the time required for force during a sustained maximal voluntary contraction to decline to 60% of maximal, was reduced in the patients compared to controls (40 +/- 14 vs. 77 +/- 29 s; P less than 0.02). There were highly significant relationships between systemic exercise performance and skeletal muscle endurance at 90 and 180 deg/s in the patients with CHF (r = 0.90 and 0.66, respectively). These findings indicate that skeletal muscle endurance is impaired in patients with CHF, that this abnormality is in part independent of limb blood flow, and that these changes may be important determinants of systemic exercise performance.

1,25-Dihydroxyvitamin D3 and muscle strength in the elderly: a randomized controlled trial

An unexplained loss of muscle strength occurs with aging. Vitamin D deficiency can cause myopathy and administration of 1,25-dihydroxyvitamin D3 [1,25-(OH2)D3] to persons with low serum concentrations can improve strength. To test the hypothesis that the weakness associated with aging is in part due to inadequate serum concentrations of [1,25-(OH2)D3], we conducted a randomized, controlled, double blinded trial in 98 men and women volunteers over 69 yr old. Treatment consisted of 0.25 micrograms 1,25-(OH)2D3, orally, twice per day or identical placebo for 6 months. Leg muscle strength of the quadriceps was measured with an isokinetic dynamometer. There was no difference between the two groups at 1 week, 1 month, or 6 months of treatment in any of the measures of muscle strength. We conclude that oral administration of 0.5 micrograms 1,25-(OH)2D3/day does not improve muscle strength in older persons. Further research is needed to determine the etiology of the decline in muscle strength associated with aging.

Rotations of Bahiagrass and Castorbean with Peanut for the Management of Meloidogyne arenaria

The relative value of 'Hale' castorbean (Ricinus communis) and 'Pensacola' bahiagrass (Paspalum notatum) as rotational crops for the management of Meloidogyne arenaria and southern blight (Sclerotium rolfsii) in 'Florunner' peanut (Arachis hypogaea) production was studied for 3 years in a field experiment in southeast Alabama. Peanut following 2 years of castorbean (C-C-P) yielded 43% higher than monocultured peanut without nematicide. At-plant application of aldicarb (30.5 g a.i./100 m row in a 20-cm-wide band) to monocultured peanut resulted in an average 38.9% increase in yield over the 3 years of the experiment. Peanut yield following 2 years of bahiagrass (B-B-P) was 36% higher than monocultured peanut without nematicide. Aldicarb application had no effect on southern blight, but both C-C-P and B-B-P rotations reduced the incidence of the disease in peanut. Juvenile populations of M. arenaria in soil at peanut harvest time were lower in plots with C-C-P than in those with the B-B-P rotation, and both rotations resulted in lower numbers of juveniles in soil than in the untreated monocultured peanut.

Cotton as a Rotation Crop for the Management of Meloidogyne arenaria and Sclerotium rolfsii in Peanut

The value of cotton (Gossypium hirsutum cv. Deltapine 90) in rotation with peanut (Arachis hypogaea cv. Florunner) for the management of root-knot nematode (Meloidogyne arenaria) and southern blight (Sclerotium rolfsii) was studied for 6 years in a field at the Wiregrass Substation in southeast Alabama. Peanut yields following either 1 or 2 years of cotton (C-P and C-C-P, respectively) were higher than those of peanut monoculture without nematicide [P(-)]. At-plant application of aldicarb to continuous peanut [P(+)] averaged 22.1% higher yields than those for P(-) over the 6 years of the study. The use of aldicarb in cotton and peanut in the C-C-P rotations increased yields of both crops over the same rotations without the nematicide. When the nematicide was applied to both crops in the C-P rotation, peanut yields were increased in only two of the possible three years when peanut was planted. Application of aldicarb to cotton only in the C-P rotation did not improve peanut yields over those obtained with the rotation without nematicide. Juvenile populations of M. arenaria determined at peanut-harvest time were lowest in plots with cotton. Plots with C-P or C-C-P had lower populations of the nematode than those with either P(-) or P(+). The incidence of southern blight (Sclerotium rolfsii) in peanut was lower in plots with the rotations than in those with peanut monoculture. Aldicarb application had no effect on the occurrence of southern blight.

Muscle-specific accumulation of Drosophila myosin heavy chains: a splicing mutation in an alternative exon results in an isoform substitution

We show that the molecular lesions in two homozygousviable mutants of the Drosophila muscle myosin heavy chain gene affect an alternative exon (exon 9a) which encodes a portion of the myosin head that is highly conserved among both cytoplasmic and muscle myosins of all organisms. In situ hybridization and Northern blotting analysis in wild-type organisms indicates that exon 9a is used in indirect flight muscles whereas both exons 9a and 9b are utilized in jump muscles. Alternative exons 9b and 9c are used in other larval and adult muscles. One of the mutations in exon 9a is a nonsense allele that greatly reduces myosin RNA stability. It prevents thick filament accumulation in indirect flight muscles and severely reduces the number of thick filaments in a subset of cells of the jump muscles. The second mutation affects the 5' splice site of exon 9a. This results in production of an aberrantly spliced transcript in indirect flight muscles, which prevents thick filament accumulation. Jump muscles of this mutant substitute exon 9b for exon 9a and consequently have normal levels of thick filaments in this muscle type. This isoform substitution does not obviously affect the ultrastructure or function of the jump muscle. Analysis of this mutant illustrates that indirect flight muscles and jump muscles utilize different mechanisms for alternative RNA splicing.

Asymmetric growth of the lateral cerebral ventricle in infants with posthemorrhagic ventricular dilation

Lateral cerebral ventricular volume in 36 preterm infants with or without an intraventricular hemorrhage, and with or without posthemorrhagic hydrocephalus, was measured longitudinally and compared with the ventricular index measurements of the same ventricles. A poor correlation was found (r2 = 0.67). To determine a reason for this poor relationship, we analyzed the volumes of the regions of the ventricles by a segmental volume analysis. The occipital region of the lateral cerebral ventricle enlarged at a much faster rate (1.904 +/- 0.477 ml/day) than either the anterior region (0.546 +/- 0.253 ml/day; p less than 0.01) or the middle region (-0.209 +/- 0.334 ml/day; p less than 0.01) in infants with posthemorrhagic hydrocephalus. The rate of growth of the middle region of the lateral cerebral ventricles was the same for all infants. Linear indexes, such as the ventricular index and the lateral ventricular ratio, do not allow for accurate serial estimates of ventricular size in posthemorrhagic hydrocephalus because of asymmetric growth of the lateral cerebral ventricle. We conclude that sequential volume measurements are more useful than ventricular index measurements to follow ventricular size sequentially in infants with posthemorrhagic hydrocephalus.

Measurement of progressive cerebral ventriculomegaly in infants after grades III and IV intraventricular hemorrhages

To develop guidelines that might help predict prospectively which infants with severe intraventricular hemorrhage (IVH) would require intervention, we obtained serial cranial sonograms to measure the rate of growth of cerebral ventricular volumes in 48 preterm infants with and without IVH. The infants were divided into three groups: (1) those with no IVH (22 infants), (2) those with IVH with acute ventricular dilation (13 infants), and (3) those with IVH with progressive ventricular dilation requiring intervention (13 infants). The decision to intervene because of progressive ventricular dilation was based on clinical criteria and the subjective assessment of increasing ventricular size on weekly cranial sonograms. The rate of cerebral ventricular volume growth in infants with IVH who needed intervention was greater (4.2 +/- 3.3 ml/day) than that in infants without IVH (0.0 +/- 0.1 ml/day; p less than 0.001) and in infants with IVH and acute ventricular dilation (0.0 +/- 0.2 ml/day; p less than 0.001). Using these data, we generated guidelines for predicting prospectively which infants with IVH and ventricular dilation will need intervention for posthemorrhagic hydrocephalus. The guidelines were then confirmed prospectively in 10 infants.

Crops Uncommon to Alabama for the Management of Meloidogyne arenaria in Peanut

In a 1987 field study juveniles of Meloidogyne arenaria assayed at the time of peanut harvest were almost undetectable in plots planted with American jointvetch (Aeschynomene americana), castor bean (Ricinus communis), partridge pea (Cassia fasiculata), sesame (Sesamum indicum), and cotton (Gossypium hirsutum), whereas plots with peanut (Arachis hypogaea) averaged 120 juveniles/100 cm(3) soil. Application of aldicarb in peanut resulted in an average of 27 juveniles/100 cm(3) soil. In 1988 all plots were planted to peanut and the aldicarb treatment was repeated in plots that had the nematicide in 1987. In 1988 peanut yields from plots that had no peanut in 1987 were 51-69% higher than the yield from those with continuous peanut and no nematicide. Aldicarb resulted in a 57% increase in yield, which is comparable to 1-year rotation to a nonhost crop. In 1988 harvest-time M. arenaria juvenile population densities in soil were the lowest in plots that had castor bean in 1987; however, the partridge pea-peanut and the sesame-peanut rotations also reduced numbers of juveniles when compared with continuous peanut with no nematicide. The aldicarb treatment resulted in juvenile population densities equivalent to those found with either the partridge pea or the sesame rotations. Rotations with American joint vetch or cotton did not result in lower juvenile population densities in peanut in 1988.

Preliminary results of a double-blind, randomized, placebo-controlled trial of cyclosporine in myasthenia gravis

We randomly assigned 20 patients with progressively worsening generalized myasthenia gravis of recent onset whose illness was not controlled by anticholinesterase therapy to treatment with either cyclosporine (6 mg per kilogram of body weight per day) or placebo. Patients who had been treated with thymectomy, steroids, or other immunosuppressive agents were excluded. The duration of treatment was 12 months. Disease activity was assessed by quantified strength testing and by measurements of antihuman acetylcholine-receptor antibody. Patients were assessed at 6 months and 12 months, or at the following early end points: drug failure (doubling of creatinine), treatment failure (respiratory or swallowing difficulty), or protocol violation (stopping medication for more than five days). At six months, patients in the cyclosporine group had had significantly more objective improvement in strength; one early end point had been reached (drug failure; no treatment failures). In the placebo group, three early end points had been reached (all treatment failures). The decline in titers of acetylcholine-receptor antibody was larger in the treated group, although the difference was not statistically significant. At the end of the study (after 12 months of treatment or arrival at an earlier end point), improvement in strength and reduction in titers of anti-receptor antibody continued to be greater in the cyclosporine group. Nephrotoxicity occurred in three patients receiving cyclosporine but was nonprogressive with a reduction in dosage and reversible with discontinuation of the drug. These results are preliminary and need confirmation, but we conclude that cyclosporine is probably an effective therapy in some patients with myasthenia gravis.

HLA and C4 polymorphism in diabetic microangiopathy

We have reported an increased frequency of the rare B3 allotype of the fourth component of complement (C4B3) in insulin-dependent diabetics, especially in those with microangiopathy. This study has now been expanded--20 of 106 subjects with microangiopathy and 9 of 116 without possessed the C4B3 allotype (p less than 0.02). C4B3 is said to be in linkage disequilibrium with HLA-DR4. HLA typing was performed on 94 of these patients, 52 with and 42 without microangiopathy. There was no significant difference in the frequency of DR4 (62 vs 50%), DR3 (65 vs 52%), B8 (40 vs 40%) or B15 (32 vs 19%) respectively between these 2 groups. These results confirm an HLA-linked predisposition to microangiopathy, but do not determine whether the primary association is with C4B3, DR4 or another gene with which they are in linkage disequilibrium.

X-linked mesangiocapillary glomerulonephritis

Two related male patients with mesangiocapillary glomerulonephritis (MCGN) are described demonstrated by renal biopsy, inherited as an X-linked disorder. Family investigations failed to reveal any underlying immunological defects or a marker for the female carrier state. The age at diagnosis, the result of discovery of proteinuria on routine urine testing during infancy, is earlier than in any other reported cases of MCGN. This raises the possibility that this variety of MCGN may develop in utero and be detectable by alpha-fetoprotein maternal screening.

Genetically determined low C4: a predisposing factor to autoimmune chronic active hepatitis

Of 26 patients with autoimmune chronic active hepatitis (CAH) starting in childhood 18 (69%) had low C4 and 5 (19%) had low C3 serum levels. Impaired hepatic synthesis and immune-consumption were unlikely since transferrin levels were normal in all patients, albumin levels were persistently low in only 3, and only 3 had raised levels of activation fragment C3d. C4d was normal in all patients studied. In the families of 12 probands with low C4, 7 parents had low C4 and 2 had levels which were at the lower limit of normal. 5 of 10 siblings from 5 families had low C4. These results suggest that low C4 levels in CAH are genetically determined. C4 phenotyping in 20 patients and in 26 parents showed that 90% and 81%, respectively, had null allotypes at either the C4A or C4B locus compared with 59% in controls, indicating that defective expression of structural genes may contribute to the observed C4 deficiency.

Factors governing the human immune response to injected insulin

Seventy-nine patients were observed prospectively during their initial period of treatment with conventional bovine insulins. Insulin antibody levels 6 months after starting insulin therapy did not correlate with age, gender or beta cell function at onset of treatment. Patients who required soluble insulin in addition to isophane insulin developed higher levels of insulin antibody. Patients bearing the HLA-B8, DR3 and C4AQO alleles had lower levels of insulin antibody, whereas those bearing DR7 produced significantly higher levels. Other alleles at the C4A, C4B, C2, factor B or Gm loci did not appear to have a significant effect on insulin antibody production. The hyporesponsiveness of B8/DR3/ C4AQO -positive individuals probably reflects a non-specific abnormality of immunity whereas the enhanced responsiveness of those positive for DR7 suggests the presence of a specific immune response gene for insulin.

Penicillamine-induced myasthenia in rheumatoid arthritis: its clinical and genetic features

The clinical features and genetic background of 18 patients with rheumatoid arthritis were investigated following the development of penicillamine-induced myasthenia (PIM). The initial myasthenia symptoms in all patients consisted of variable diplopia and/or ptosis with progression to a more generalized involvement in 7 of them. No clinical, humoral, or genetic factor was determined which would allow identification of individuals developing generalized as opposed to ocular myasthenia. Withdrawal of penicillamine was associated over 4-60 weeks with a slow resolution of symptoms, facilitated in 12 patients by the use of anticholinesterase agents. In 2 patients a persistent partial unilateral ptosis remains after 15 and 25 months, while in a further patient diplopia is present 42 months after resolution of the other myasthenic symptoms. The patients with PIM when compared with a healthy 'control' population had a significant increase in HLA Dr1 (p corr less than 0.005) and an absence of HLA Dr 3. A genetic susceptibility to the development of PIM, distinct from that observed in myasthenia gravis of spontaneous onset, is suggested by this abnormal distribution of HLA Dr antigens.