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The metabolic activation of polycyclic aromatic hydrocarbons (PAH), for example benzo[a]pyrene, leads to the formation of carcinogen-macromolecular adducts. Methods that make it possible to detect low levels of these adducts in human peripheral blood samples should be useful in the dosimetry of human exposure to carcinogens. We demonstrated previously the usefulness of enzyme immunoassays and of synchronous fluorescence spectroscopy (SFS) for detecting and characterizing low levels of PAH-macromolecular adducts present in synthetic adduct mixtures. These methods have now been refined and applied to the analysis of samples of peripheral blood collected from occupationally exposed individuals (coke-oven workers) and from people attending smoking cessation clinics. The results of both immunoassays and SFS show the presence of benzo[a]pyrene diol epoxide (BPDE)-DNA, BPDE-haemoglobin and other putative PAH-macromolecular adducts in peripheral blood samples from certain individuals.

The techniques of molecular and harmonic dynamics are used to study the internal mobility of three double-stranded DNA hexamers. A 60 ps molecular dynamics simulation and a normal mode description of d(CpGpCpGpCpG)2 in the B conformation characterize the atomic fluctuations of this structure. A comparison between the two approaches validates the harmonic results at room temperature. Detailed examination of the normal modes indicates that only the low-frequency modes are needed to determine atomic fluctuations. A harmonic analysis is made of d(CpGpCpGpCpG)2 in the Z conformation and of d(TpApTpApTpA)2 in the B conformation using only the low-frequency modes. The atomic fluctuations of the three alternating pyrimidine-purine helices are compared and the dependence on conformation and sequence are discussed. The insights which theoretical calculations can provide for the interpretation of experimental results are explored.

Three-dimensional computer models for two segments of the C terminus of gp41, the transmembrane AIDS envelope protein, which may form amphipathic alpha-helices, have been generated using structure prediction techniques combined with energy minimization and molecular dynamics simulations. Regions gp41(772-790) and gp41(828-848) of the HXB2 strain of HIV-1 display extraordinarily high hydrophobic moment maxima as alpha-helices and when in an antiparallel conformation exhibit charge complementarity, implying that they may bind with each other and associate with the membrane. The feasibility of this hypothesis was tested in a series of computer simulations of these peptides, extended by several residues to include additional charge pairing. Beginning with a trial structure in the form of antiparallel alpha-helices of segments 770-794 and 824-856, systematic axial rotations and displacements were used to generate alternative initial states. Molecular dynamics simulations with alpha-helical torsional restraints yielded several approximately cylindrical dimeric structures highly stabilized by numerous salt links and other hydrogen bonds. This suggests that these two regions may fold back on each other in antiparallel fashion to form a loop in the tertiary structure over residues 770-856, with the loop closed by membrane-associated amphipathic alpha-helices with charged sides facing each other. We speculate that such structures could aggregate to form channels or otherwise destabilize the membrane, thereby contributing to the cytopathic effects of the gp120-gp41 complex.

Three measures of lower extremity function were compared in a homogenous population of ALS patients. Isokinetic dynamometry was shown to be a sensitive tool for change in strength over time. It demonstrated positive correlations with gait velocity as well as other behavioral measures. Manual muscle tests were relatively insensitive and no more reliable than isokinetics. Isokinetics are a useful adjunct in the assessment of ALS.

Molecular dynamics simulations of hen egg-white lysozyme in the free and substrate-bound states are reported and the nature of the average structures and atomic fluctuations are analyzed. Crystallographic water molecules of structural importance, as determined by hydrogen-bonding, were included in the simulations. Comparisons are made between the dynamics and the X-ray results for the atomic positions, the main-chain and side-chain dihedral angles, and the hydrogen-bonding geometry. Improvements over earlier simulations in the potential energy function and methodology resulted in stable trajectories with the C alpha co-ordinates within 1.5 A of the starting X-ray structure. Structural features analyzed in the simulations agreed well with the X-ray results except for some surface residues. The Asx chi 2 dihedral distribution and the geometry of hydrogen bonding at reverse turns show differences; possible causes are discussed. The relation between the magnitudes and time-scales of the residue fluctuations and secondary structural features, such as helices beta-sheets and coiled loops, is examined. Significant differences in the residue mobilities between the simulations of the free and substrate-bound states were found in a region of the enzyme that is in direct contact with the substrate and in a region that is distant from the active-site cleft. The dynamic behavior of the structural water molecules is analyzed by examining the correlation between the fluctuations of the water oxygens and the lysozyme heavy-atoms to which they are hydrogen-bonded.

Thyrotropin-releasing hormone (TRH) metabolism in NIH:N mouse cerebral cortex and spinal cord was studied with high pressure liquid chromatography. Degradation of added TRH was significantly (P less than 0.001) slower in the spinal cord (2.19 +/- 0.46%/min) than in the cerebral cortex (7.54 +/- 0.31%/min). Bacitracin, a non-competitive inhibitor of TRH deamidase, inhibited TRH degradation by 61.3 +/- 3.7% in the spinal cord but only by 35.9 +/- 1.0% in the cerebral cortex (P less than 0.001). Catabolism of TRH in the mouse spinal cord proceeds at a slower rate and predominantly via the TRH deamidase pathway.

The prevalence and nature of emotional disturbance in patients with multiple sclerosis (MS) was studied prospectively in 64 MS patients and 23 spinal cord-injured (SCI) control patients by administration of the 28-item subscale General Health Questionnaire (GHQ). MS patients in remission had a mean GHQ score of 4.4, and patients with acute exacerbation or progressive nonremitting MS had a mean score of 15.7, a significant difference (p less than 0.001). The prevalence of emotional disturbance was 90% in exacerbating or progressing patients, 39% in stable patients, and 12% in SCI control patients. The presence of emotional disturbance was not related to age, sex, or other demographic variables, to duration or severity of disease, or to the degree of disability. In the group of MS patients in remission, somatic complaints, anxiety, and social dysfunction were more prevalent than symptoms of depression.

Eighty-seven patients with definite multiple sclerosis (MS) were examined neurologically and administered the Mini-mental State examination (MMS) to assess cognitive disability at the beginning and end of a one-year study. A CT scan was performed in 37. A group of 16 patients with stable spinal cord injuries (SCI) were studied in a similar manner. Of the MS patients, 47% had a mean General Health Questionnaire (GHQ) score in the abnormal range. This was a higher rate than in SCI patients (P = 0.004). Mean depression scores were similar in MS and SCI patients, but MS patients with brain involvement were more depressed than those with cord lesions only (P = 0.05). Depression score was unrelated to functional disability but was correlated with the degree of neurological impairment (P = 0.03). Euphoric patients were more likely to have brain involvement (P = 0.006), to have progressive MS (P less than 0.0001), and to have enlarged ventricles (P = 0.04) and were more impaired cognitively (P = 0.04) than noneuphoric patients. These results suggest that depression in MS patients is partly determined by the presence of brain involvement, but that it is also an emotional reaction to the disorder. Euphoria and cognitive disorder are reflections of brain involvement.

Lumbar cerebrospinal fluid (CSF) gamma-aminobutyric acid (GABA) levels determined by fluorometric assay in four seizure patients were found to be significantly lower during bilateral, continuous cerebellar stimulation than those determined after a 7-day period without stimulation. The CSF GABA concentrations during chronic unilateral, alternating cerebellar stimulation were reduced in three seizure patients but unchanged in a fourth patient. The percentage decrease in CSF GABA appeared to be independent of cerebellar stimulation frequency. These findings suggest that GABA-mediated neuronal transmission is depressed during cerebellar surface stimulation and this evoked reduction in GABA activity may compromise the efficacy of cerebellar stimulation in the treatment of epilepsy. Lumbar CSF cyclic guanosine monophosphate levels determined by radioimmunoassay were not significantly altered by either mode or frequency of cerebellar stimulation.

Focal, small-to-moderate and transient improvement occurred in the muscle strength and function of patients with ALS who received TRH in dose-response and screening studies. In a small pilot study of 12 patients, 3 months administration of TRH at 10 mg per kg on alternate days resulted in localized increased strength of jaw muscles as well as significant improvement in lower extremity function. Aerobic exercise capacity was particularly improved in patients with ALS following administration of TRH. Autonomic effects of TRH on heart rate, respiration, and blood pressure were not serious and attenuated slightly over the course of the study.

PML is a progressive opportunistic infection of the CNS caused by a commonly occurring virus that may become manifest in the context of reduced host resistance in persons of any age. The authors review the disease and its causes, including a discussion of treatment attempts and differential diagnoses.

Heart rate, respiratory rate, systolic and diastolic blood pressure, and oral and skin temperature changes following intravenous administration of TRH occur at lower infusion rates in patients with ALS and bulbar involvement than in patients with ALS without bulbar involvement. This autonomic sensitivity to TRH infusion is characteristic of a more advanced stage of ALS with difficulties in speaking and swallowing. Patients who will be receiving neuropeptides, such as TRH, must be carefully studied to determine whether subclinical bulbar involvement is present. Such patients may require a lower initial dose or dose rate adjustment as well as continual monitoring during neuropeptide administration.

A new NMR method is described for the generation of absorption mode two-dimensional NOE spectra of oligonucleotides in H2O solution. The method yields spectra that are free of baseline distortions with excellent suppression of the intense H2O resonance. The method is demonstrated for a sample of the dodecamer d(CGCGAATTCGCG)2. All exchangeable base protons are identified and a number of new types of NOE connectivities are observed.

The primary amino acid structure of the lysozyme-binding antibody, HyHEL-10, as determined by amino acid and nucleotide sequencing was utilized to construct a scale model of the Fv (variable region domain of immunoglobulin) using energy-minimized torsional angles of the McPC603 Fv as a prototype template. This model was in turn used as a template for generating a computer-built set of co-ordinates, which were subjected to a total of 600 steps of Adopted Basis Newton-Raphson energy minimizations using the program CHARMM. Only minimal shifts of the backbone (root-mean-square 0.76 A) were required to give an energetically stable structure with a favorable van der Waals' energy. Several notable features were evident from both the scale model and the energy-minimized computer model: (1) the shape of the antibody combining region is that of a very shallow concavity approximately 20 A X 25 A; (2) the concavity is acidic and non-hydrophobic and is bordered by hydrophobic segments; (3) the lower portion of the combining site is dominated by a cluster of tyrosine residues over the L3 and H2 areas; (4) a somatic mutation encoded by the J region of the heavy chain (JH) may contribute significantly to the complementarity of heavy chain H3 to the epitope on hen egg white lysozyme. In addition, the space-filling energy-minimized model revealed that residue 49L, a framework residue, was prominently exposed and accessible in the center of the combining-site concavity. The model suggests that variation in length of complementarity-determining regions may function not only to change directly the shape of the antibody combining site, but may also influence indirectly the nature of the antibody surface by changing the accessibility of residues not usually involved in antigen binding.

This paper considers the effects of truncating long-range forces on protein dynamics. Six methods of truncation that we investigate as a function of cutoff criterion of the long-range potentials are (1) a shifted potential; (2) a switching function; (3) simple atom-atom truncation based on distance; (4) simple atom-atom truncation based on a list which is updated periodically (every 25 steps); (5) simple group-group truncation based on distance; and (6) simple group-group truncation based on a list which is updated periodically (every 25 steps). Based on 70 calculations of carboxymyoglobin we show that the method and distance of long range cutoff have a dramatic effect on overall protein behavior. Evaluation of the different methods is based on comparison of a simulation's rms fluctuation about the average coordinates, the rms deviation from the average coordinates of a no cutoff simulation and from the X-ray structure of the protein. The simulations in which long-range forces are truncated by a shifted potential shows large rms deviations for cutoff criteria less than 14 A, and reasonable deviations and fluctuations at this cutoff distance or larger. Simulations using a switching function are investigated by varying the range over which electrostatic interactions are switched off. Results using a short switching function that switches off the potential over a short range of distances are poor for all cutoff distances. A switching function over a 5-9 A range gives reasonable results for a distance-dependent dielectric, but not using a constant dielectric. Both the atom-atom and group-group truncation methods based on distance shows large rms deviation and fluctuation for short cutoff distances, while for cutoff distances of 11 A or greater, reasonable results are achieved. Although comparison of these to distance-based truncation methods show surprisingly larger rms deviations for the group-group truncation, contrary to simulation studies of aqueous ionic solutions. The results of atom-atom or group-group list-based simulations generally appear to be less stable than the distance-based simulations, and require more frequent velocity scaling or stronger coupling to a heat bath.

Immunoreactive myelin basic protein (MBP) levels were measured in cerebrospinal fluid (CSF) samples taken from 57 patients with active hydrocephalus (age range 3 weeks to 60 years). Of these patients, 28 (49%) had elevated MBP values (greater than 4.5 ng/ml). Elevated MBP levels were found in 44% of patients with congenital hydrocephalus, 75% of patients with posttraumatic hydrocephalus, 80% of patients with normal-pressure hydrocephalus, and 83% of patients with porencephaly. Also associated with abnormal MBP levels was the ventricular size as measured by computerized tomography scanning (chi 2: p less than 0.05): 36% of the patients with small ventricles (ventricle:brain ratio 0 to 0.4:1) had elevated MBP in the CSF, whereas 61% of those with moderate ventricles (0.41 to 0.6:1 ratio) and 100% of those with large ventricles (0.61 to 0.85:1 ratio) had abnormal values. Only 33% of those with maximal hydrocephalus (0.86 to 1.0:1 ratio) had elevated MBP levels, perhaps because of dilution effects. In three patients in whom CSF was obtained simultaneously by ventricular and lumbar punctures, the ventricular fluid had a consistently higher concentration of MBP, suggesting a cerebral origin. It is concluded that active hydrocephalus produces significant periventricular demyelination, probably as the result of mechanical stretching.

Acute multifocal posterior placoid pigment epitheliopathy (APMPPE) is an unusual self-limited retinal disorder that has been associated with various systemic complications. To our knowledge, three prior cases associated with cerebral vasculitis have been described. This article describes a patient with APMPPE and angiographically documented cerebral vasculitis who was notable because of (a) the presence of two different cerebral ischemic events, occurring 1 month apart, and (b) the long latency (3 months) between the onset of ocular symptoms and the second cerebral ischemic event. Recognition of the association between APMPPE and cerebral vasculitis may permit early treatment of CNS involvement and prevention of morbidity.

Decreased cerebrospinal fluid concentrations of cyclic nucleotides in human motor neuron disease and decreased spinal cord concentrations of cyclic nucleotides in murine (Wobbler) motor neuron disease suggest that an abnormality in cyclic nucleotide metabolism may play a role in motor neuron degeneration. Retroviruses cause decreased cellular levels of cyclic nucleotides in infected cells. We induced a motor neuron degeneration with a neurotropic retrovirus, but not with a non-neurotropic retrovirus. In paralyzed mice, mean cAMP was decreased 21% in posterior horn segments and 34% in anterior horn segments compared to controls. The proportion of spinal cord phosphorylase a decreased 24% in paralyzed mice compared to controls. The content of cGMP decreased 48% in the cerebellum and 25% in both anterior and posterior horn segments of the spinal cords of paralyzed mice compared to controls. White matter content of these chemicals did not decrease in the posterior column of affected animals. Spinal cord content of ATP increased 20-22% in all three compartments, but the spinal cord content of phosphocreatine increased dramatically in white matter (46%), posterior horn gray matter (69%), and anterior horn gray matter (103%) compared to controls. Changes in high-energy phosphate intermediate and cyclic nucleotide metabolites occurred only in topographical regions showing neuronal and astrocyte pathological changes, but did not occur in the cerebral cortex.