A novel CDK9-associated C-type cyclin interacts directly with HIV-1 Tat and mediates its high-affinity, loop-specific binding to TAR RNA

The HIV-1 Tat protein regulates transcription elongation through binding to the viral TAR RNA stem-loop structure. We have isolated a novel 87 kDa cyclin C-related protein (cyclin T) that interacts specifically with the transactivation domain of Tat. Cyclin T is a partner for CDK9, an RNAPII transcription elongation factor. Remarkably, the interaction of Tat with cyclin T strongly enhances the affinity and specificity of the Tat:TAR RNA interaction, and confers a requirement for sequences in the loop of TAR that are not recognized by Tat alone. Moreover, overexpression of human cyclin T rescues Tat activity in nonpermissive rodent cells. We propose that Tat directs cyclin T-CDK9 to RNAPII through cooperative binding to TAR RNA.

A cellular DNA-binding protein that activates eukaryotic transcription and DNA replication

Transcription factor CTF, which is responsible for selective recognition of eukaryotic promoters that contain the sequence CCAAT, was purified to apparent homogeneity by sequence-specific DNA affinity chromatography. Binding sites for CTF in the human Ha-ras and alpha-globin promoters were highly homologous to sequences recognized by nuclear factor I (NF-I), a cellular DNA-binding protein that is required for the initiation of adenovirus DNA replication in vitro. To determine the relationship between CTF and NF-I, we compared the biochemical properties of these two proteins. CTF and NF-I were found to be indistinguishable in polypeptide composition, DNA-binding properties, immunological cross-reactivity, and in vitro stimulation of DNA replication and transcription initiation. We conclude that CTF/NF-I can serve both as a transcription selectivity factor for RNA polymerase II and as an initiation factor for adenovirus DNA replication.

GABA(B) receptors function as a heteromeric assembly of the subunits GABA(B)R1 and GABA(B)R2

The principal inhibitory neurotransmitter GABA (gamma-aminobutyric acid) exerts its effects through two ligand-gated channels, GABA(A) and GABA(C) receptors, and a third receptor, GABA(B) , which acts through G proteins to regulate potassium and calcium channels. Cells heterologously expressing the cloned DNA encoding the GABA(B)R1 protein exhibit high-affinity antagonist-binding sites, but they produce little of the functional activity expected from studies of endogenous GABA(B) receptors in the brain. Here we describe a new member of the GABA(B) polypeptide family, GABA(B)R2, that shows sequence homology to GABA(B)R1. Neither GABA(B)R1 nor GABA(B)R2, when expressed individually, activates GIRK-type potassium channels; however, the combination of GABA(B)R1 and GABA(B)R2 confers robust stimulation of channel activity. Both genes are co-expressed in individual neurons, and both proteins co-localize in transfected cells. Moreover, immunoprecipitation experiments indicate that the two polypeptides associate with each other, probably as heterodimers. Several G-protein-coupled receptors (GPCRs) exist as high-molecular-weight species, consistent with the formation of dimers by these receptors, but the relevance of these species for the functioning of GPCRs has not been established. We have now shown that co-expression of two GPCR structures, GABA(B)R1 and GABA(B)R2, belonging to the same subfamily is essential for signal transduction by GABA(B) receptors.

Trace amines: identification of a family of mammalian G protein-coupled receptors

Tyramine, beta-phenylethylamine, tryptamine, and octopamine are biogenic amines present in trace levels in mammalian nervous systems. Although some "trace amines" have clearly defined roles as neurotransmitters in invertebrates, the extent to which they function as true neurotransmitters in vertebrates has remained speculative. Using a degenerate PCR approach, we have identified 15 G protein-coupled receptors (GPCR) from human and rodent tissues. Together with the orphan receptor PNR, these receptors form a subfamily of rhodopsin GPCRs distinct from, but related to the classical biogenic amine receptors. We have demonstrated that two of these receptors bind and/or are activated by trace amines. The cloning of mammalian GPCRs for trace amines supports a role for trace amines as neurotransmitters in vertebrates. Three of the four human receptors from this family are present in the amygdala, possibly linking trace amine receptors to affective disorders. The identification of this family of receptors should rekindle the investigation of the roles of trace amines in mammalian nervous systems and may potentially lead to the development of novel therapeutics for a variety of indications.

Validity and reliability of a postoperative quality of recovery score: the QoR-40

Quality of recovery after anaesthesia is an important measure of the early postoperative health status of patients. We attempted to develop a valid, reliable and responsive measure of quality of recovery after anaesthesia and surgery. We studied 160 patients and asked them to rate postoperative recovery using three methods: a 100-mm visual analogue scale (VAS), a nine-item questionnaire and a 50-item questionnaire; the questionnaires were repeated later on the same day. From these results, we developed a 40-item questionnaire as a measure of quality of recovery (QoR-40; maximum score 200). We found good convergent validity between QoR-40 and VAS (r = 0.68, P < 0.001). Construct validity was supported by a negative correlation with duration of hospital stay (rho = -0.24, P < 0.001) and a lower mean QoR-40 score in women (162 (SD 26)) compared with men (173 (17)) (P = 0.002). There was also good test-retest reliability (intra-class ri = 0.92, P < 0.001), internal consistency (Cronbach's alpha = 0.93, P < 0.001) and split-half coefficient (alpha = 0.83, P < 0.001). The standardized response mean, a measure of responsiveness, was 0.65. The QoR-40 was completed in less than 6.3 (4.9) min. We believe that the QoR-40 is a good objective measure of quality of recovery after anaesthesia and surgery. It would be a useful end-point in perioperative clinical studies.

Activation of the AIDS retrovirus promoter by the cellular transcription factor, Sp1

The nature and position of transcriptional control elements responsible for the expression of genes encoded by the retrovirus associated with acquired immune deficiency syndrome (AIDS) have not been precisely defined. In this study it is shown that the mammalian Sp1 transcription factor binds to promoter sequences within the AIDS retrovirus long terminal repeat (LTR) and activates RNA synthesis five- to eightfold in reconstituted reactions in vitro. Experiments in which regions of DNA were protected from added reagents by specifically bound proteins (footprinting) indicated that the upstream promoter region of the AIDS virus LTR lies between -45 and -77 (relative to the RNA start site, +1) and contains three tandem, closely spaced SP1 binding sites of variable affinity. Base-substitution mutations targeted to one or all three Sp1 binding sites were found both to eliminate the binding of Sp1 and to cause up to a tenfold reduction in transcriptional efficiency in vitro. These findings suggest that one important component of the AIDS virus transcriptional control region interacts with a cellular transcription factor, Sp1, and that this factor must function in conjunction with transcriptional elements located downstream of the RNA cap site to mediate the response of the LTR to viral trans-activation.

Prediction of femoral fracture load using automated finite element modeling

Hip fracture is an important cause of morbidity and mortality among the elderly. Current methods of assessing a patient's risk of hip fracture involve local estimates of bone density (densitometry), and are limited by their inability to account for the complex structural features of the femur. In an effort to improve clinical and research tools for assessing hip fracture risk, this study investigated whether automatically generated, computed tomographic (CT) scan-based finite element (FE) models can be used to estimate femoral fracture load in vitro. Eighteen pairs of femora were examined under two loading conditions one similar to loading during the stance phase of gait, and one simulating impact from a fall. The femora were then mechanically tested to failure and regression analyses between measured fracture load and FE-predicted fracture load were performed. For comparison, densitometry measures were also examined. Significant relationships were found between measured fracture load and FE-predicted fracture load (r = 0.87, stance; r = 0.95, fall; r = 0.97, stance and fall data pooled) and between measured fracture load and densitometry data (r = 0.78, stance; r = 0.91, fall). These results indicate that this sophisticated technique, which is still early in its development, can achieve precision comparable to that of densitometry and can predict femoral fracture load to within -40% to +60% with 95% confidence. Therefore, clinical use of this approach, which would require additional X-ray exposure and expenditure for a CT scan, is not justified at this point. Even so, the potential advantages of this CT/FE technique support further research in this area.

MRI measures of entorhinal cortex vs hippocampus in preclinical AD

BACKGROUND

MRI measures of the entorhinal cortex and the hippocampus have been used to predict which nondemented individuals with memory problems will progress to meet criteria for AD on follow-up, but their relative accuracy remains controversial.

OBJECTIVES

To compare MRI measures of the entorhinal cortex and the hippocampus for predicting who will develop AD.

METHODS

MRI volumes of the entorhinal cortex and the hippocampus were obtained in 137 individuals comprising four groups: 1) individuals with normal cognition both at baseline and after 3 years of follow-up (n = 28), 2) subjects with memory difficulty but not dementia both at baseline and after 3 years of follow-up (n = 73), 3) subjects with memory difficulty at baseline who were diagnosed with probable AD within 3 years of follow-up (n = 21), and 4) patients with mild AD at baseline (n = 16).

RESULTS

Measures of both the entorhinal cortex and the hippocampus were different for each of the pairwise comparisons between the groups (p < 0.001) and were correlated with tests of memory (p < 0.01). However, the volume of the entorhinal cortex differentiated the subjects from those destined to develop dementia with considerable accuracy (84%), whereas the measure of the hippocampus did not.

CONCLUSION

These findings are consistent with neuropathologic data showing substantial involvement of the entorhinal cortex in the preclinical phase of AD and suggest that, as the disease spreads, atrophic change develops within the hippocampus, which is measurable on MRI.

Identification and characterization of two G protein-coupled receptors for neuropeptide FF

The central nervous system octapeptide, neuropeptide FF (NPFF), is believed to play a role in pain modulation and opiate tolerance. Two G protein-coupled receptors, NPFF1 and NPFF2, were isolated from human and rat central nervous system tissues. NPFF specifically bound to NPFF1 (K(d) = 1.13 nm) and NPFF2 (K(d) = 0.37 nm), and both receptors were activated by NPFF in a variety of heterologous expression systems. The localization of mRNA and binding sites of these receptors in the dorsal horn of the spinal cord, the lateral hypothalamus, the spinal trigeminal nuclei, and the thalamic nuclei supports a role for NPFF in pain modulation. Among the receptors with the highest amino acid sequence homology to NPFF1 and NPFF2 are members of the orexin, NPY, and cholecystokinin families, which have been implicated in feeding. These similarities together with the finding that BIBP3226, an anorexigenic Y1 receptor ligand, also binds to NPFF1 suggest a potential role for NPFF1 in feeding. The identification of NPFF1 and NPFF2 will help delineate their roles in these and other physiological functions.

The interaction between HIV-1 Tat and human cyclin T1 requires zinc and a critical cysteine residue that is not conserved in the murine CycT1 protein

HIV-1 Tat activates transcription through binding to human cyclin T1, a regulatory subunit of the TAK/P-TEFb CTD kinase complex. Here we show that the cyclin domain of hCycT1 is necessary and sufficient to interact with Tat and promote cooperative binding to TAR RNA in vitro, as well as mediate Tat transactivation in vivo. A Tat:TAR recognition motif (TRM) was identified at the carboxy-terminal edge of the cyclin domain, and we show that hCycT1 can interact simultaneously with Tat and CDK9 on TAR RNA in vitro. Alanine-scanning mutagenesis of the hCycT1 TRM identified residues that are critical for the interaction with Tat and others that are required specifically for binding of the complex to TAR RNA. Interestingly, we find that the interaction between Tat and hCycT1 requires zinc as well as essential cysteine residues in both proteins. Cloning and characterization of the murine CycT1 protein revealed that it lacks a critical cysteine residue (C261) and forms a weak, zinc-independent complex with HIV-1 Tat that greatly reduces binding to TAR RNA. A point mutation in mCycT1 (Y261C) restores high-affinity, zinc-dependent binding to Tat and TAR in vitro, and rescues Tat transactivation in vivo. Although overexpression of hCycT1 in NIH3T3 cells strongly enhances transcription from an integrated proviral promoter, we find that this fails to overcome all blocks to productive HIV-1 infection in murine cells.

Context, composition and heterogeneity: using multilevel models in health research

This paper considers the use of multilevel models in health research. Attention focuses on the structure and potential of such models and particular consideration is given to their use in elucidating the importance of contextual effects in relation to individual level social and demographic factors in understanding health outcomes, health-related behaviour and health service performance. Four graphical typologies are used to outline the questions that multilevel models can address and the paper illustrates their potential by drawing on published examples in a number of different research areas.

Preclinical prediction of AD using neuropsychological tests

Normals (N = 42) and patients with mild memory difficulty (N = 123) were given a neuropsychological test battery, and then followed annually for 3 years to determine which individuals developed sufficient functional change that they met clinical criteria for AD. Twenty-three of the 123 participants with mild memory difficulty converted to a diagnosis of probable Alzheimer's disease (AD) within 3 years of follow-up. Four of the 20 neuropsychological measures obtained at baseline, were useful in discriminating the groups on the basis of their status 3 years after the tests were given. The 4 discriminating tests pertained to assessments of memory and executive function. When the controls were compared to the individuals with memory impairments who ultimately developed AD (the converters), the accuracy of discrimination was 89%, based on the neuropsychological measures at baseline. The discrimination of the controls from the individuals with mild memory problems who did not progress to the point where they met clinical criteria for probable AD over the 3 years of follow-up (the Questionables) was 74% and the discrimination of the questionables from the converters was 80%. The specific tests that contributed to these discriminations, in conjunction with recent neuropathological and neuroimaging data from preclinical cases, have implications for which brain regions may be affected during the prodromal phase of AD.

Preclinical prediction of Alzheimer's disease using SPECT

BACKGROUND

Regional cerebral perfusion measured by single photon emission computed tomography (SPECT) was examined as a preclinical predictor of the development of Alzheimer's disease (AD).

METHODS

Singular value decomposition was used to produce 20 SPECT factors (known as vectors) (n=152). Vector scores were then computed for four groups (n=136), differing in cognitive status: Group 1--normal controls at both baseline and follow-up; Group 2--subjects with "questionable" AD at both baseline and follow-up; Group 3--subjects with questionable AD at baseline who converted to AD on follow-up (Converters); Group 4--subjects with AD at baseline. All SPECT data in the analyses were gathered at baseline.

RESULTS

The four groups could be distinguished on the basis of their baseline SPECT data (p < or = 0.00005; hit rate=83%). Regional decreases in perfusion were most prominent among Converters in the hippocampal-amygdaloid complex, the posterior cingulate, the anterior thalamus, and the anterior cingulate. Inclusion of apolipoprotein E status did not significantly improve the discrimination.

CONCLUSIONS

SPECT data gathered and analyzed in this manner may be useful as one aspect of the preclinical prediction of AD. Three of the four brain regions important for discriminating Converters from normal controls involve a distributed brain network pertaining to memory, suggesting that this network may be selectively affected in the earliest stages of AD.

Inhibition of axonal growth by SNAP-25 antisense oligonucleotides in vitro and in vivo

Axonal elongation and the transformation of growth cones to synaptic terminals are major steps of brain development and the molecular mechanisms involved form the basis of the correct wiring of the nervous system. The same mechanisms may also contribute to the remodelling of nerve terminals that occurs in the adult brain, as a morphological substrate to memory and learning. We have investigated the function of the nerve terminal protein SNAP-25 (ref. 2) during development. We report here that SNAP-25 is expressed in axonal growth cones during late stages of elongation and that selective inhibition of SNAP-25 expression prevents neurite elongation by rat cortical neurons and PC-12 cells in vitro and by amacrine cells of the developing chick retina in vivo. These results demonstrate that SNAP-25 plays a key role in axonal growth. They also suggest that high levels of SNAP-25 expression in specific areas of the adult brain may contribute to nerve terminal plasticity.

Evidence for placental abnormality as the major cause of mortality in first-trimester somatic cell cloned bovine fetuses

The production of cloned animals is, at present, an inefficient process. This study focused on the fetal losses that occur between Days 30-90 of gestation. Fetal and placental characteristics were studied from Days 30-90 of gestation using transrectal ultrasonography, maternal pregnancy specific protein b (PSPb) levels, and postslaughter collection of fetal tissue. Pregnancy rates at Day 30 were similar for recipient cows carrying nuclear transfer (NT) and control embryos (45% [54/120] vs. 58% [11/19]), although multiple NT embryos were often transferred into recipients. From Days 30-90, 82% of NT fetuses died, whereas all control pregnancies remained viable. Crown-rump (CR) length was less in those fetuses that were destined to die before Day 90, but no significant difference was found between the CR lengths of NT and control fetuses that survived to Day 90. Maternal PSPb levels at Days 30 and 50 of gestation were not predictive of fetal survival to Day 90. The placentas of six cloned and four control (in vivo or in vitro fertilized) bovine pregnancies were compared between Days 35 and 60 of gestation. Two cloned placentas showed rudimentary development, as indicated by flat, cuboidal trophoblastic epithelium and reduced vascularization, whereas two others possessed a reduced number of barely discernable cotyledonary areas. The remaining two cloned placentas were similar to the controls, although one contained hemorrhagic cotyledons. Poor viability of cloned fetuses during Days 35-60 was associated with either rudimentary or marginal chorioallantoic development. Our findings suggest that future research should focus on factors that promote placental and vascular growth and on fetomaternal interactions that promote placental attachment and villous formation.

The scientific rediscovery of an ancient Chinese herbal medicine: Cordyceps sinensis: part I

This review presents Cordyceps sinensis (Berk.) Sacc., a fungus highly valued in China as a tonic food and herbal medicine. The extant records show the continued use of C. sinensis is now centuries old. The major chemical, pharmacological, and toxicological studies on C. sinensis and the various derived, cultured, fermented mycelial products currently in use are reviewed from the English and Chinese literature. Preclinical in vitro and in vivo studies and clinical blinded or open-label trials in to date over 2000 patients are reviewed. These studies show the main activities of the fungus in oxygen-free radical scavenging, antisenescence, endocrine, hypolipidemic, antiatherosclerotic, and sexual function-restorative activities. The safety of the fungus, its effects on the nervous system, glucose metabolism, the respiratory, hepatic, cardiovascular, and immune systems, immunologic disease, inflammatory conditions, cancer, and diseases of the kidney will be reviewed in the second part of this article to be published in the winter issue of this journal.

A thymus-specific member of the HMG protein family regulates the human T cell receptor C alpha enhancer

The human T cell-specific transcription factor TCF-1 alpha plays a key role in the tissue-specific activation of the T cell receptor (TCR) C alpha enhancer and binds to pyrimidine-rich elements (5'-PyCTTTG-3') present in a variety of other T cell-specific control regions. Using amino acid sequence information derived from the DNA affinity-purified protein, we have now isolated cDNA clones encoding TCF-1 alpha. The TCF-1 alpha cDNA contains a single 68-amino-acid domain that is homologous to a region conserved among high-mobility group (HMG) and nonhistone chromosomal proteins. Expression of full-length and mutant cDNA clones in bacteria reveal that the single HMG motif, which is predicted to contain two extended alpha-helical segments, is sufficient to direct the sequence-specific binding of TCF-1 alpha to DNA. Northern blot experiments demonstrate further that TCF-1 alpha mRNA is highly tissue specific, found primarily in the thymus or T cell lines. The immature CEM T cell line expresses relatively low levels of TCF-1 alpha mRNA, which are increased upon activation of these cells by phorbol esters. Interestingly, the cloned TCF-1 alpha protein is a potent transcriptional activator of the human TCR alpha enhancer in nonlymphoid cell lines, whereas the activity of the endogenous protein in T cell lines is strongly dependent on an additional T cell-specific protein that interacts with the core enhancer. TCF-1 alpha is currently unique among the newly emerging family of DNA-binding regulatory proteins that share the HMG motif in that it is a highly tissue-specific RNA polymerase II transcription factor.

Predictors of cognitive change in older persons: MacArthur studies of successful aging

This study used a linear structural relations modeling technique (LISREL) to examine longitudinal data for 1,192 persons from a community-based population. The goal was to test the ability of an a priori model to predict cognitive change over a 2.0- to 2.5-year period in older adults aged 70-79 at the initial evaluation. The model included 22 demographic, physical, and psychosocial variables as predictors of cognitive function and cognitive change. The study used an exploratory-confirmatory design, enabling cross-validation of the model developed in the exploratory set in the confirmatory sample. Structural equation modeling analyses identified 4 endogenous model variable (education, strenuous activity, peak pulmonary expiratory flow rate, and self-efficacy) as direct predictors of cognitive change over the study period.

Frontal lobe function, sleep loss and fragmented sleep

Recent experimental studies involving total sleep loss, sleep reduction and clinically related sleep fragmentation report impaired performance on tasks of frontal lobe or executive function, including measures of verbal fluency, creativity and planning skills. Severity of sleep disturbance in obstructive sleep apnoea syndrome (OSAS) is correlated with level of executive impairment, with some residual impairment despite treatment (continuous positive airway pressure - CPAP). Executive impairment appears to be more closely related to hypoxaemic events rather than daytime sleepiness. Studies of electroencephalographic (EEG) changes throughout the course of sleep and following sleep deprivation as well as functional neuroimaging and psychophysiological changes (event-related potentials - ERPs) following sleep deprivation provide further indication of the relative importance of the frontal regions of the brain to sleep. However, neurocognitive studies present many inconsistencies, task classification is often ambiguous and, in the absence of any unifying explanation at the level of cognitive mechanisms, the overall picture is one of a disparate range of impairment following sleep loss and sleep fragmentation. Poorly defined concepts of frontal lobe function, executive function, memory and attention, using tasks largely developed with more severe deficit levels in mind, create further difficulties in interpreting current findings.

Sequence and analysis of chromosome 4 of the plant Arabidopsis thaliana

The higher plant Arabidopsis thaliana (Arabidopsis) is an important model for identifying plant genes and determining their function. To assist biological investigations and to define chromosome structure, a coordinated effort to sequence the Arabidopsis genome was initiated in late 1996. Here we report one of the first milestones of this project, the sequence of chromosome 4. Analysis of 17.38 megabases of unique sequence, representing about 17% of the genome, reveals 3,744 protein coding genes, 81 transfer RNAs and numerous repeat elements. Heterochromatic regions surrounding the putative centromere, which has not yet been completely sequenced, are characterized by an increased frequency of a variety of repeats, new repeats, reduced recombination, lowered gene density and lowered gene expression. Roughly 60% of the predicted protein-coding genes have been functionally characterized on the basis of their homology to known genes. Many genes encode predicted proteins that are homologous to human and Caenorhabditis elegans proteins.

Hydroxyapatite cement. I. Basic chemistry and histologic properties

Hydroxyapatite cement is a unique calcium phosphate preparation that can be shaped intraoperatively and sets in vivo to an implant composed of microporous hydroxyapatite. The histologic response to this cement was evaluated by implanting disks made of this material within the heads of nine cats. Three sets of 12 hydroxyapatite cement disks were produced containing 0%, 10%, and 20% macropores by volume, respectively. The disks were implanted subcutaneously, intramuscularly, above the periosteum of the skull, and directly onto the surface of the calvarium. Each macropore percentage was represented in each tissue plane, and animals were killed up to 9 months postoperatively. There were no toxic reactions, implants extruded, or wound infections. Histologic examination of the implant-soft-tissue interfaces revealed a transient inflammatory response without foreign body reaction. The disks were resorbed over time in direct proportion to their macropore content (surface areas) in all groups except for those disks placed directly onto the surface of the calvarium below the periosteum. In this group, numerous foci of bone formed at the skull-implant interface, with variable replacement of the deep surface of these implants by bone. Implant replacement by bone is postulated to occur through a combination of implant resorption coupled with osteoconduction. Based on these properties, hydroxyapatite cement may prove useful when applied to the reconstruction of non-stress-bearing skeletal tissue.

Structural arrangements of transcription control domains within the 5'-untranslated leader regions of the HIV-1 and HIV-2 promoters

Promoter-proximal downstream regions of the human immunodeficiency viruses (HIV-1 and HIV-2) mediate the action of the viral transcription activator protein, Tat. We demonstrate here that the downstream domain of each virus interacts with two RNA polymerase II transcription factors. One of these, CTF/NF I, is a multifunctional protein associated previously with activation of transcription and DNA replication. The other cellular protein, designated LBP-1 (leader-binding protein-1), recognizes repeated elements within an extended region of DNA corresponding to part of the 5'-untranslated leader. Analysis of clustered point mutants in the HIV-1 leader for DNA-binding and transcription activity in vitro and in vivo suggests a role for LBP-1 as part of the basal promoter. A complex overlapping arrangement is observed between sequences required for the interaction of LBP-1 and CTF/NF I proteins and those defined previously for regulation by the HIV-1 Tat protein.