Drawing improves memory in patients with hippocampal damage.

The hippocampus plays a critical role in the formation of declarative memories, and hippocampal damage leads to significant impairments in new memory formation. Drawing can serve as a form of multi-modal encoding that improves declarative memory performance relative to other multimodal encoding strategies such as writing. We examined whether, and to what extent, patients with hippocampal damage could benefit from the mnemonic strategy of drawing. Three patients with focal hippocampal damage, and one patient with both hippocampal and cortical lesions, in addition to 22 age-, sex-, and education-matched controls, were shown a list of words one at a time during encoding and instructed to either draw a picture or repeatedly write each word for 40 s. Following a brief filled delay, free recall and recognition memory for words from both encoding trial types were assessed. Controls showed enhanced recall and recognition memory for words drawn versus those that were written, an effect that was even more pronounced in patients with focal hippocampal damage. By contrast, the patient with both hippocampal and cortical lesions showed no drawing-mediated boost in either recall or recognition memory. These findings demonstrate that drawing is an effective encoding strategy, likely accruing from the engagement of extra-hippocampal processes including the integration of cortical-based motor, visual, and semantic processing, enabling more elaborative encoding.

Temporal Construal Effects Are Independent of Episodic Future Thought.

Human thought is prone to biases. Some biases serve as beneficial heuristics to free up limited cognitive resources or improve well-being, but their neurocognitive basis is unclear. One such bias is a tendency to construe events in the distant future in abstract, general terms and events in the near future in concrete, detailed terms. Temporal construal may rely on our capacity to orient toward and/or imagine context-rich future events. We tested 21 individuals with impaired episodic future thinking resulting from lesions to the hippocampus or ventromedial prefrontal cortex (vmPFC) and 57 control participants (aged 45-76 years) from Canada and Italy on measures sensitive to temporal construal. We found that temporal construal persisted in most patients, even those with impaired episodic future thinking, but was abolished in some vmPFC cases, possibly in relation to difficulties forming and maintaining future intentions. The results confirm the fractionation of future thinking and that parts of vmPFC might critically support our ability to flexibly conceive and orient ourselves toward future events.

Quantitative Assessment of the Risk of Release of Foot-and-Mouth Disease Virus via Export of Bull Semen from Israel.

Various foot-and-mouth disease (FMD) virus strains circulate in the Middle East, causing frequent episodes of FMD outbreaks among Israeli livestock. Since the virus is highly resistant in semen, artificial insemination with contaminated bull semen may lead to the infection of the receiver cow. As a non-FMD-free country with vaccination, Israel is currently engaged in trading bull semen only with countries of the same status. The purpose of this study was to assess the risk of release of FMD virus through export of bull semen in order to estimate the risk for FMD-free countries considering purchasing Israeli bull semen. A stochastic risk assessment model was used to estimate this risk, defined as the annual likelihood of exporting at least one ejaculate of bull semen contaminated with viable FMD virus. A total of 45 scenarios were assessed to account for uncertainty and variability around specific parameter estimates and to evaluate the effect of various mitigation measures, such as performing a preexport test on semen ejaculates. Under the most plausible scenario, the annual likelihood of exporting bull semen contaminated with FMD virus had a median of 1.3 * 10-7 for an export of 100 ejaculates per year. This corresponds to one infected ejaculate exported every 7 million years. Under the worst-case scenario, the median of the risk rose to 7.9 * 10-5 , which is equivalent to the export of one infected ejaculate every 12,000 years. Sensitivity analysis indicated that the most influential parameter is the probability of viral excretion in infected bulls.

DNA binding and 3'-5' exonuclease activity in the murine alternatively-spliced p53 protein.

In this study we show that the naturally occurring C-terminally alternative spliced p53 (referred to as AS-p53) is active as a sequence-specific DNA binding protein as well as a 3'-5'-exonuclease in the presence of Mg2+ ions. The two activities are positively correlated as the sequence-specific DNA target is more efficiently degraded than a non-specific target. In contrast, a mutated AS-p53 protein that is deficient in DNA binding lacks exonuclease activity. The use of modified p53 binding sites, where the 3'-phosphate is replaced by a phosphorothioate group, enabled the inhibition of DNA degradation under the binding conditions. We demonstrate that AS-p53 interacts with its specific DNA target by two distinct binding modes: a high-affinity mode characterized by a low-mobility protein-DNA complex at the nanomolar range, and a low-affinity mode shown by a high-mobility complex at the micromolar range. Comparison of the data on the natural and the modified p53 binding sites suggests that the high-affinity mode is related to AS-p53 function as a transcription factor and that the low-affinity mode is associated with its exonuclease activity. The implications of these findings to a specific cellular role of AS-p53 are discussed.

NADP-dependent bacterial alcohol dehydrogenases: crystal structure, cofactor-binding and cofactor specificity of the ADHs of Clostridium beijerinckii and Thermoanaerobacter brockii.

We have determined the X-ray structures of the NADP(H)-dependent alcohol dehydrogenase of Clostridiim beijerinckii (CBADH) in the apo and holo-enzyme forms at 2.15 A and 2.05 A resolution, respectively, and of the holo-alcohol dehydrogenase of Thermoanaerobacter brockii (TBADH) at 2.5 A. These are the first structures of prokaryotic alcohol dehydrogenase to be determined as well as that of the first NADP(H)-dependent alcohol dehydrogenase. CBADH and TBADH 75% have sequence identity and very similar three-dimensional structures. Both are tetramers of 222 symmetry. The monomers are composed of two domains: a cofactor-binding domain and a catalytic domain. These are separated by a deep cleft at the bottom of which a single zinc atom is bound in the catalytic site. The tetramers are composed of two dimers, each structurally homologous to the dimer of alcohol dehydrogenases of vertebrates. The dimers form tetramers by means of contacts between surfaces opposite the interdomain cleft thus leaving it accessible from the surface of the tetramer. The tetramer encloses a large internal cavity with a positive surface potential. A molecule of NADP(H) binds in the interdomain cleft to the cofactor-binding domain of each monomer. The specificity of the two bacterial alcohol dehydrogenases toward NADP(H) is determined by residues Gly198, Ser199, Arg200 and Tyr218, with the latter three making hydrogen bonds with the 2'-phosphate oxygen atoms of the cofactor. Upon NADP(H) binding to CBADH, Tyr218 undergoes a rotation of approximately 120 degrees about chi1 which facilitates stacking interactions with the adenine moiety and hydrogen bonding with one of the phosphate oxygen atoms. In apo-CBADH the catalytic zinc is tetracoordinated by side-chains of residues Cys37, His59, Asp150 and Glu60; in holo-CBADH, Glu60 is retracted from zinc in three of the four monomers whereas in holo-TBADH, Glu60 does not participate in Zn coordination. In both holo-enzymes, but not in the apo-enzyme, residues Ser39 and Ser113 are in the second coordination sphere of the catalytic zinc. The carboxyl group of Asp150 is oriented with respect to the active carbon of NADP(H) so as to form hydrogen bonds with both pro-S and pro-R hydrogen atoms.

Oligomeric integrity--the structural key to thermal stability in bacterial alcohol dehydrogenases.

Principles of protein thermostability have been studied by comparing structures of thermostable proteins with mesophilic counterparts that have a high degree of sequence identity. Two tetrameric NADP(H)-dependent alcohol dehydrogenases, one from Clostridium beijerinckii (CBADH) and the other from Thermoanaerobacter brockii (TBADH), having exceptionally high (75%) sequence identity, differ by 30 degrees in their melting temperatures. The crystal structures of CBADH and TBADH in their holo-enzyme form have been determined at a resolution of 2.05 and 2.5 A, respectively. Comparison of these two very similar structures (RMS difference in Calpha = 0.8 A) revealed several features that can account for the higher thermal stability of TBADH. These include additional ion pairs, "charged-neutral" hydrogen bonds, and prolines as well as improved stability of alpha-helices and tighter molecular packing. However, a deeper structural insight, based on the location of stabilizing elements, suggests that enhanced thermal stability of TBADH is due mainly to the strategic placement of structural determinants at positions that strengthen the interface between its subunits. This is also supported by mutational analysis of structural elements at critical locations. Thus, it is the reinforcement of the quaternary structure that is most likely to be a primary factor in preserving enzymatic activity of this oligomeric bacterial ADH at elevated temperatures.

Enhanced thermal stability of Clostridium beijerinckii alcohol dehydrogenase after strategic substitution of amino acid residues with prolines from the homologous thermophilic Thermoanaerobacter brockii alcohol dehydrogenase.

A comparison of the three-dimensional structures of the closely related mesophilic Clostridium beijerinckii alcohol dehydrogenase (CBADH) and the hyperthermophilic Thermoanaerobacter brockii alcohol dehydrogenase (TBADH) suggested that extra proline residues in TBADH located in strategically important positions might contribute to the extreme thermal stability of TBADH. We used site-directed mutagenesis to replace eight complementary residue positions in CBADH, one residue at a time, with proline. All eight single-proline mutants and a double-proline mutant of CBADH were enzymatically active. The critical sites for increasing thermostability parameters in CBADH were Leu-316 and Ser-24, and to a lesser degree, Ala-347. Substituting proline for His-222, Leu-275, and Thr-149, however, reduced thermal stability parameters. Our results show that the thermal stability of the mesophilic CBADH can be moderately enhanced by substituting proline at strategic positions analogous to nonconserved prolines in the homologous thermophilic TBADH. The proline residues that appear to be crucial for the increased thermal stability of CBADH are located at a beta-turn and a terminating external loop in the polypeptide chain. Positioning proline at the N-caps of alpha-helices in CBADH led to adverse effects on thermostability, whereas single-proline mutations in other positions in the polypeptide had varying effects on thermal parameters. The finding presented here support the idea that at least two of the eight extra prolines in TBADH contribute to its thermal stability.

Longitudinal MRI study of hippocampal volume in trauma survivors with PTSD.

OBJECTIVE: The authors prospectively explored whether a reduction in the volume of the hippocampus occurs in recent trauma survivors who develop posttraumatic stress disorder (PTSD). METHOD: Thirty-seven survivors of traumatic events were assessed within a week of the traumatic event and 6 months later. The assessment included magnetic resonance imaging of the brain (including 124 coronal slices of 1.5-mm thickness), psychometric testing, and structured clinical interviews. The Clinician-Administered PTSD Scale conferred PTSD diagnoses at 6 months. RESULTS: Ten subjects (27%) had PTSD at 6 months. The subjects with PTSD did not differ from those without PTSD in hippocampal volume (right or left) at 1 week or 6 months. There was no reduction in hippocampal volume in the PTSD subjects between 1 week and 6 months. CONCLUSIONS: Smaller hippocampal volume is not a necessary risk factor for developing PTSD and does not occur within 6 months of expressing the disorder. This brain abnormality might occur in individuals with chronic or complicated PTSD.

A rapid and robust particle-enhanced turbidimetric immunoassay for serum beta 2 microglobulin.

A rapid particle-enhanced turbidimetric immunoassay (PETIA), for the measurement of serum beta 2-microglobulin is described. The method has a working range of 0.2-40 mg/l, with good precision and a correlation coefficient of 0.97 when compared with an established radioimmunoassay method. One of the major advantages of this assay is the stability of the calibration curve (up to at least 20 months). This, and the fact that no pretreatment of serum samples is necessary, makes the assay ideally suited for all types of routine determination.

Demographic characteristics of patients with community-acquired bacteriuria and susceptibility of urinary pathogens to antimicrobials in northern Israel.

BACKGROUND: Urinary tract infection is one of the most common bacterial infections. Since antibiotics are given empirically, it is necessary to assess the distribution and susceptibility of the microorganisms in each case. OBJECTIVES: To evaluate the demographic characteristics of ambulatory patients with UTI, the distribution and susceptibility of uropathogens, and the risk factors associated with trimethoprim-sulfamethoxazole resistant bacteria in women. METHODS: During 12 days in August 1997 all the urine cultures sent to the Tel-Hanan Laboratory (Haifa) were evaluated. Demographic characteristics of the patients, their underlying diseases and the previous use of antibiotics were obtained. RESULTS: During the 12 day survey 6,495 cultures were sent for evaluation. Of the 1,075 (17%) that were positive 950 were included in the study; 83.7% were from females, of whom 57% were > or = 50 years old. Escherichia coli was the most common pathogen, with 74.7% in the female and 55% in the male population; 86.2% of the E. coli were resistant to amoxicillin, 38.8% to cephalexin and 46.8% to TMP-SMX. Cefuroxime (4.2%), ofloxacin (4.8%), ciprofloxacin (4.8%) and nitrofurantoin (0.4%) showed the lowest rates of resistance. By a multivariant analysis, post-menopause and recurrent UTI were found to be independent factors related to TMP-SMX resistance in women. CONCLUSION: In northern Israel, ampicillin, cephalexin and TMP-SMX cannot be used empirically in the treatment of community-acquired UTI. Post-menopause and recurrent UTI are independent factors associated with TMP-SMX resistant pathogens in women.

Criterion validation of premorbid intelligence estimation in persons with traumatic brain injury: "hold/don't hold" versus "best performance" procedures.

The goal of the present study was to validate previously suggested regression equations for the estimation of premorbid ability against a real premorbid intellectual criterion. Fifty-four patients with traumatic brain injuries, for whom a premorbid military Primary Psychometric Rating (PPR) was available, participated in the study. Two prediction procedures were validated: (a) "BEST-10", which generates a predicted score from the highest observed score of 10 WAIS-R subtests, according to the "best performance" estimation principle. (b) "BEST-2", which generates the predicted score from the higher of two subtests considered a priori resistant to neurological damage according to the "hold/don't hold" principle. The two procedures showed similar correlation with the premorbid criterion. However, the BEST-10 method provided a more accurate estimation, generating a non-significant 2-point underestimation. The results support the application of previously proposed equations for estimating premorbid intelligence, and suggest that the use of the best performance principle is preferable as compared to the hold/don't hold principle.

Traumatic brain injury (TBI) 10-20 years later: a comprehensive outcome study of psychiatric symptomatology, cognitive abilities and psychosocial functioning.

The goal of this study was to measure the very long-term mental and psychosocial outcomes of severe traumatic brain injury (TBI). Seventy-six persons with severe TBI were evaluated extensively by means of standardized scales, neuropsychological tests and evaluations by family members, at an average of 14.1 (SD = 5.5) years post-injury. Six mental and functional domains were examined: psychiatric symptomatology, cognitive abilities, vocational status, family integration, social functioning, and independence in daily routines. The findings indicate a long-term differential effect of severe TBI, with seriously affected psychiatric symptomatology, family and social domains, as compared to moderately influenced cognitive, vocational and independent functioning. Relatively high rates of depression, psychomotor slowness, loneliness and family members' sense of burden were found. In addition to their epidemiological importance, the results indicate that persons with TBI and their families may need professional assistance to maintain a reasonable psychosocial quality of life, even more than a decade post-injury.

Proton positions in the Mn(2+) binding site of concanavalin A as determined by single-crystal high-field ENDOR spectroscopy.

High-field (95 GHz) pulsed EPR and electron-nuclear double resonance (ENDOR) techniques have been used for the first time to determine coordinates of ligand protons of a high-spin metal center in a protein single crystal. The protein concanavalin A contains a Mn(2+) ion which is coordinated to two water molecules, a histidine residue, and three carboxylates. Single crystals of concanavalin A were grown in H(2)O and in D(2)O to distinguish the exchangeable water protons from the nonexchangeable protons of the imidazole group. Distinct EPR transitions were selected by performing the ENDOR measurements at different magnetic fields within the EPR spectrum. This selection, combined with the large thermal polarization achieved at 4.5 K and a magnetic field of approximately 3.4 T allowed us to assign the ENDOR signals to their respective M(S) manifolds, thus providing the signs of the hyperfine couplings. Rotation patterns were acquired in the ac and ab crystallographic planes. Two distinct crystallographic sites were identified in each plane, and the hyperfine tensors of two of the imidazole protons and the four water protons were determined by simulations of the rotation patterns. All protons have axially symmetric hyperfine tensors and, by applying the point-dipole approximation, the positions of the various protons relative to the Mn(2+) ion were determined. Likewise, the water protons involved in H-bonding to neighboring residues were identified using the published, ultrahigh-resolution X-ray crystallographic coordinates of the protein (Deacon et al. J. Chem. Soc., Faraday Trans. 1997, 93(24), 4305-4312).

Structures of furanosides: geometrical analysis of low-temperature X-ray and neutron crystal structures of five crystalline methyl pentofuranosides.

Crystal structures of all five crystalline methyl D-pentofuranosides, methyl alpha-D-arabinofuranoside (1), methyl beta-D-arabinofuranoside (2), methyl alpha-D-lyxofuranoside (3), methyl beta-D-ribofuranoside (4) and methyl alpha-D-xylofuranoside (5) have been determined by means of cryogenic X-ray and neutron crystallography. The neutron diffraction experiments provide accurate, unbiased H-atom positions which are especially important because of the critical role of hydrogen bonding in these systems. This paper summarizes the geometrical and conformational parameters of the structures of all five crystalline methyl pentofuranosides, several of them reported here for the first time. The methyl pentofuranoside structures are compared with the structures of the five crystalline methyl hexopyranosides for which accurate X-ray and neutron structures have been determined. Unlike the methyl hexopyranosides, which crystallize exclusively in the C(1) chair conformation, the five crystalline methyl pentofuranosides represent a very wide range of ring conformations.