Diurnal and dietary-induced changes in cholesterol synthesis correlate with levels of mRNA for HMG-CoA reductase

We determined the extent to which diurnal variation in cholesterol synthesis in liver is controlled by steady-state mRNA levels for the rate-limiting enzyme in the pathway, hydroxymethylglutaryl (HMG)-CoA reductase. Rats 30 days of age and maintained on a low-cholesterol diet since weaning were injected intraperitoneally with (3)H(2)O. The specific radioactivity of the whole-body water pool soon became constant, allowing for expression of values for incorporation of label into cholesterol as absolute rates of cholesterol synthesis. In liver, there was a peak of cholesterol synthesis from 8 pm to midnight, a 4-fold increase over synthesis rates from 8 am to noon. Increases in synthesis were quantitatively in lock step with increases in mRNA levels for HMG-CoA reductase occurring 4 h earlier. In a parallel experiment, rats received 1% cholesterol in the diet from weaning to 30 days of age. Basal levels of hepatic cholesterol synthesis were greatly diminished and there was little diurnal variation of cholesterol synthesis or of levels of mRNA for HMG-CoA reductase. Levels of mRNA for the low density lipoprotein receptor and scavenger receptor-B1 (putative high density lipoprotein receptor) showed little diurnal variation, regardless of diet. This suggests that diurnal variation of hepatic cholesterol synthesis is driven primarily by varying the steady-state mRNA levels for HMG-CoA reductase. Other tissues were also examined. Adrenal gland also showed a 4-fold diurnal increase in accumulation of recently synthesized cholesterol. In contrast to liver, however, there was little corresponding change in mRNA expression for HMG-CoA reductase. Much of this newly synthesized cholesterol may be of hepatic origin, imported into adrenal by SR-B1, whose mRNA was up-regulated 2-fold. In brain, there was no diurnal variation in either cholesterol synthesis or mRNA expression, and no influence of high- or low-cholesterol diets on synthesis rates or HMG-CoA reductase mRNA levels.

Expression of p300-truncated fragments results in the modulation of apoptosis in rat mesangial cells

BACKGROUND

Mesangial cell proliferation, apoptosis, and matrix deposition have pivotal roles in the pathogenesis of renal diseases such as diabetic nephropathy and glomerulonephritis. The behavior of mesangial cells depends on the integration of intracellular signals elicited by hormones and cytokines. We hypothesized that p300 is primarily involved in the integration of signal transduction pathways in rat mesangial cells (RMCs) and that interference with p300 function will alter apoptotic signals.

METHODS

We established an RMC cell line expressing the Tet-activator (tTA). RMC-tTA cells were transiently transfected with vectors coding for either the N-terminal third or the C-terminal third of p300. Expression was induced by the addition of doxycycline [Dox; 1 microg/mL; 5% fetal bovine serum (FBS)]. The percentage of apoptosis was determined using the TUNEL technique. Specific protein-protein interactions were determined by Western blot analysis of immunoprecipitated complexes. Cells were treated with 5% FBS or with H2O2 (500 micromol/L, 1 h) with and without Dox.

RESULTS

The expression of p300-C resulted in increased susceptibility to low serum-induced (20.0 +/- 4.6 vs. 3.0 +/- 1.7%) and to H2O2-induced apoptosis (75.3 +/- 13.3 vs. 50.8 +/- 6.5%) compared with controls. Immunoprecipitation of p300-C showed an interaction with the transcription factor c-Fos, which was enhanced by H2O2 treatment. Expression of the p300-N resulted in a rescue (34.8 +/- 6. 4 vs. 50.8 +/- 6.5%) from H2O2-induced apoptosis compared with controls. P300-N was shown to form a complex with the transcription factor nuclear factor-kappaB (NF-kappaB).

CONCLUSIONS

The data indicate that endogenous p300 is involved in apoptosis in mesangial cells. We propose that interference or enhancement of endogenous p300 function, by expression of exogenous fragments, can alter interactions with c-Fos or NF-kappaB and modulate signals during cellular stress.

Predicting protein structure using only sequence information

This paper presents results of blind predictions submitted to the CASP3 protein structure prediction experiment. We made predictions using the SAM-T98 method, an iterative hidden Markov model-based method for constructing protein family profiles. The method is purely sequence-based, using no structural information, and yet was able to predict structures as well as all but five of the structure-based methods in CASP3.

Dual efficacy of lamivudine treatment in human immunodeficiency virus/hepatitis B virus-coinfected persons in a randomized, controlled study (CAESAR). The CAESAR Coordinating Committee

The efficacy and safety of lamivudine in persons coinfected with human immunodeficiency virus (HIV) type 1 and hepatitis B virus (HBV) were examined in the CAESAR study, a randomized placebo-controlled trial assessing the addition of lamivudine (150 mg 2x/day) or lamivudine (150 mg 2x/day) plus loviride (100 mg 3x/day) to zidovudine-containing background antiretroviral treatment. Baseline hepatitis B surface antigen (HBsAg) results were available for 1790 study subjects, of whom 122 (6.8%) tested positive. Retrospective analyses for serial HBV DNA, HBsAg, and hepatitis B e antigen (HBeAg) were performed on stored sera from 118 HBsAg-positive subjects. HBV DNA and HBeAg were present in 83% and 63%, respectively. At weeks 12 and 52, median log10 HBV DNA change was -2.0 and -2.7, respectively, in the lamivudine arms, compared with no reduction among placebo recipients (P<.001). A trend to lower alanine transferase level, and delayed progression of HIV-1 disease (relative hazard, 0.26; 95% confidence interval, 0.08-0.80) were also seen in the lamivudine arms, compared with the placebo group.

Calcium influx and activation of calpain I mediate acute reactive gliosis in injured spinal cord

Buffering extracellular pH at the site of a spinal cord crush-injury may stimulate axonal regeneration in rats (1; Guth et al., Exp. Neurol. 88: 44-55, 1985). We demonstrated in cultured astrocytes that acidic pH initiates a rapid increase in immunoreactivity for GFAP (GFAP-IR), a hallmark of reactive gliosis (2; Oh et al., Glia 13: 319-322, 1995). We extended these studies by investigating the effects of certain treatments on reactive gliosis developing in situ in a rat spinal cord injury model. A significant reactive gliosis was observed within 2 days of cord lesion in untreated crush or vehicle-treated, crush control animals as evidenced by increased GFAP-IR and hypertrophy of astrocytes. By contrast, infusion of Pipes buffer (pH 7.4) into the lesion site significantly reduced this increase. The increased GFAP-IR appeared to be linked to Ca2+ influx since infusion of a blocker of L-type calcium channels, nifedipine, reduced the ensuing reactive gliosis significantly. While Ca2+ modulates many signaling pathways within cells, its effect on reactive gliosis appeared to result from an activation of calpain I. Calpain inhibitor I, a selective inhibitor of mu-calpain, also significantly reduced reactive gliosis. However, calpain inhibitor II, a close structural analog which blocks m-calpain, had no salutary effect. We suggest, therefore, that the initial reactive gliosis seen in vivo may result from the activation of a neutral, Ca2+-dependent protease, calpain I, through calcium influx.

Further clinical clarification of the muscle dysfunction in cervical headache

The Headache Classification Committee of the International Headache Society listed impairments in cervical muscle function as criteria for headaches of cervical spine origin. Fifteen subjects with cervical headache and 15 controls were tested for the frequency of abnormal responses to passive stretching and abnormal muscle contraction. A new test of cranio-cervical flexion was used to assess the contraction of the deep neck flexors. Results indicated a trend towards a higher frequency of abnormal response to passive stretching of the muscles examined in the cervical headache group but only the upper trapezius proved significantly different to the control group. Deep neck flexor muscle contraction was significantly inferior in the cervical headache group. From the perspective of physical characterization of cervical headache, it appears that response from passive stretch of muscle may not be a strong criterion for cervical headache but deep neck flexor performance may have potential to identify musculoskeletal involvement in headache. The finding may also provide positive directions for conservative treatment of cervical headache.

Hidden Markov models for detecting remote protein homologies

MOTIVATION

A new hidden Markov model method (SAM-T98) for finding remote homologs of protein sequences is described and evaluated. The method begins with a single target sequence and iteratively builds a hidden Markov model (HMM) from the sequence and homologs found using the HMM for database search. SAM-T98 is also used to construct model libraries automatically from sequences in structural databases.

METHODS

We evaluate the SAM-T98 method with four datasets. Three of the test sets are fold-recognition tests, where the correct answers are determined by structural similarity. The fourth uses a curated database. The method is compared against WU-BLASTP and against DOUBLE-BLAST, a two-step method similar to ISS, but using BLAST instead of FASTA.

RESULTS

SAM-T98 had the fewest errors in all tests-dramatically so for the fold-recognition tests. At the minimum-error point on the SCOP (Structural Classification of Proteins)-domains test, SAM-T98 got 880 true positives and 68 false positives, DOUBLE-BLAST got 533 true positives with 71 false positives, and WU-BLASTP got 353 true positives with 24 false positives. The method is optimized to recognize superfamilies, and would require parameter adjustment to be used to find family or fold relationships. One key to the performance of the HMM method is a new score-normalization technique that compares the score to the score with a reversed model rather than to a uniform null model.

AVAILABILITY

A World Wide Web server, as well as information on obtaining the Sequence Alignment and Modeling (SAM) software suite, can be found at http://www.cse.ucsc.edu/research/compbi o/

CONTACT

karplus@cse.ucsc.edu; http://www.cse.ucsc.edu/karplus

Sequence comparisons using multiple sequences detect three times as many remote homologues as pairwise methods

The sequences of related proteins can diverge beyond the point where their relationship can be recognised by pairwise sequence comparisons. In attempts to overcome this limitation, methods have been developed that use as a query, not a single sequence, but sets of related sequences or a representation of the characteristics shared by related sequences. Here we describe an assessment of three of these methods: the SAM-T98 implementation of a hidden Markov model procedure; PSI-BLAST; and the intermediate sequence search (ISS) procedure. We determined the extent to which these procedures can detect evolutionary relationships between the members of the sequence database PDBD40-J. This database, derived from the structural classification of proteins (SCOP), contains the sequences of proteins of known structure whose sequence identities with each other are 40% or less. The evolutionary relationships that exist between those that have low sequence identities were found by the examination of their structural details and, in many cases, their functional features. For nine false positive predictions out of a possible 432,680, i.e. at a false positive rate of about 1/50,000, SAM-T98 found 35% of the true homologous relationships in PDBD40-J, whilst PSI-BLAST found 30% and ISS found 25%. Overall, this is about twice the number of PDBD40-J relations that can be detected by the pairwise comparison procedures FASTA (17%) and GAP-BLAST (15%). For distantly related sequences in PDBD40-J, those pairs whose sequence identity is less than 30%, SAM-T98 and PSI-BLAST detect three times the number of relationships found by the pairwise methods.

Cardiovascular, endocrine, and body fluid-electrolyte responses to salt loading in mRen-2 transgenic rats

We previously demonstrated that mRen-2 transgenic [Tg(+)] rats are sensitive to chronic high NaCl intake, showing increased arterial pressure and vasopressin (VP) secretion. In this study, we determined the effect of a chronic osmotic challenge, 4 days of drinking 2% NaCl, on direct arterial blood pressure, heart rate, fluid-electrolyte balance, circadian rhythm of mean arterial pressure (MAP), and changes in plasma VP and catecholamines. Under baseline conditions, male Tg(+) rats showed a significant shift in the peak in circadian MAP into the light portion of the day-night cycle. Substitution of 2% NaCl for drinking water caused a rapid increase in MAP, 20 +/- 5 mmHg in Tg(+) rats within 6 h. Whereas the amplitude of circadian MAP fluctuations increased in salt-loaded Tg(+) rats, there was no significant change in the circadian timing of peak MAP with salt loading. Tg(+) rats showed exaggerated osmotic-induced increases in plasma VP, norepinephrine (NE), and epinephrine (Epi) compared with Tg(-) rats. Plasma NE and Epi were increased two- and fourfold, respectively, in the hypertensive rats with no significant change in the Tg(-) rats. Intravenous administration of a VP antagonist did not alter arterial pressure in either Tg(+) or Tg(-) rats. Tg(+) and Tg(-) rats showed a positive sodium balance with no significant difference observed between the groups. Tg(+) rats showed a significant increase in salt consumption, plasma sodium, osmolality, and hematocrit, accompanied by a negative water balance. We conclude that Tg(+) rats are sensitive to acute and chronic osmotic stimuli in terms of blood pressure, fluid-electrolyte balance, and plasma VP and catecholamines. Whereas elevated plasma VP does not contribute to the hypertensive response, increased sympathetic drive may mediate the salt-induced blood pressure changes in this model.

Monocyte chemoattractant protein 1 is responsible for macrophage recruitment following injury to sciatic nerve

Following injury to the peripheral nervous system, circulating monocytes/macrophages are recruited to the damaged tissue, where they play vital roles during both nerve degeneration and subsequent regeneration. Monocyte chemoattractant protein-1 (MCP-1), a member of the C-C or beta-chemokine family, is a powerful leukocyte recruitment/activation factor that is relatively specific for monocytes/macrophages. Because these are the predominant leukocyte type recruited by injured nerve, we hypothesized that upregulation of MCP-1 expression is involved in recruitment of these cells. Indeed, assay of steady-state levels of MCP-1 mRNA in rat sciatic nerve during tellurium-induced primary demyelination indicated up-regulation of this chemokine with a peak after 3 days of tellurium exposure, preceding the peak of accumulation of phagocytic macrophages (assayed as lysozyme mRNA levels) by 6 days. Increasing levels of MCP-1 mRNA expression, induced by increasing levels of tellurium exposure, resulted in corresponding increases in subsequent recruitment of macrophages. In situ hybridization suggested that MCP-1 mRNA was localized in Schwann cells. No expression of MIP-2, which is a C-X-C or alpha-chemokine that is specific for recruitment of neutrophils, was detected, consistent with the lack of recruitment of significant numbers of these cells. In addition, we also investigated the response seen following nerve transection (axonal degeneration and secondary demyelination with no subsequent regeneration) and nerve crush (degeneration followed by regeneration). In these latter two nerve injury models, there was also a marked, early up-regulation of MCP-1 mRNA, with a time course that is compatible with a role for this chemokine in macrophage recruitment. We conclude that MCP-1 is involved in recruiting monocytes/macrophages to injured peripheral nerve and that the specificity of leukocyte types recruited results from specificity of chemokine production.

Predicting protein structure using hidden Markov models

We discuss how methods based on hidden Markov models performed in the fold-recognition section of the CASP2 experiment. Hidden Markov models were built for a representative set of just over 1,000 structures from the Protein Data Bank (PDB). Each CASP2 target sequence was scored against this library of HMMs. In addition, an HMM was built for each of the target sequences and all of the sequences in PDB were scored against that target model, with a good score on both methods indicating a high probability that the target sequence is homologous to the structure. The method worked well in comparison to other methods used at CASP2 for targets of moderate difficulty, where the closest structure in PDB could be aligned to the target with at least 15% residue identity.

Restoring homeostasis in a residential care facility through behaviour modification

A verbally aggressive, 32-year-old male with a traumatic brain injury was admitted to a unit in an aged care facility for residential care. The homeostasis of the unit was disrupted by the resident's verbal aggression and other inappropriate behaviours. With the guidance of a neuropsychologist, nursing staff were able to use behaviour modification to successfully replace the disruptive behaviours with more socially appropriate ones. A series of positive rewards was implemented in response to socially appropriate behaviour, whilst inappropriate behaviours received a negative reward. Several disruptive behaviours were affected by the single treatment implemented. This interdependence of targeted behaviours was viewed as a clinical advantage, as it served to provide a more rapid restoration of homeostasis to the unit. The use of a single-subject, multiple baseline design in this case study demonstrates that disruptive behaviours may be reversible.

Factors leading to a strike vote and strategies for reestablishing relationships

An extremely difficult contract negotiation between a collective bargaining unit and a hospital resulted in a vote to strike by the nursing staff before reaching a final agreement. The authors describe the factors that led up to the strike vote. Realistic yet optimistic strategies for developing a working relationship with the bargaining unit leadership and the nursing staff are described.

Job satisfaction in preceptorship and its effect on the clinical performance of the preceptee

This study was designed to examine the relationship between preceptor/preceptee job satisfaction and preceptee clinical performance. A correlational descriptive design using quantitative data was employed through a mailed survey. Seventy-nine questionnaires were mailed to preceptors, 100 to preceptees. The response rate for preceptors was 49.4% while the response rate for preceptees was 33%. Herzberg's theory served as the conceptual framework. Three baccalaureate schools of nursing in Atlantic Canada comprised the setting. Analysis of data included frequencies, percentages, t-tests, and Pearson's product-moment correlation coefficient. Findings indicate that preceptors and preceptees differ significantly regarding aspects of their job, and their job in general. They also differ significantly in their rating of how often preceptees perform the planning/evaluation components of their care. A positive significant relationship exists between preceptee job satisfaction and clinical performance. No relationship was found to exist between preceptor job satisfaction and preceptee clinical performance. Additionally, in view of the limitations of the study (small sample, low response) limited conclusions can be drawn from the study.

Alterations in gene expression associated with primary demyelination and remyelination in the peripheral nervous system

Primary demyelination is an important component of a number of human diseases and toxic neuropathies. Animal models of primary demyelination are useful for isolating processes involved in myelin breakdown and remyelination because the complicating events associated with axonal degeneration and regeneration are not present. The tellurium neuropathy model has proven especially useful in this respect. Tellurium specifically blocks synthesis of cholesterol, a major component of PNS myelin. The resulting cholesterol deficit in myelin-producing Schwann cells rapidly leads to sychronous primary demyelination of the sciatic nerve, which is followed by rapid synchronous remyelination when tellurium exposure is discontinued. Known alterations in gene expression for myelin proteins and for other proteins involved in the sequence of events associated with demyelination and subsequent remyelination in the PNS are reviewed, and new data regarding gene expression changes during tellurium neuropathy are presented and discussed.

Scoring hidden Markov models

MOTIVATION

Statistical sequence comparison techniques, such as hidden Markov models and generalized profiles, calculate the probability that a sequence was generated by a given model. Log-odds scoring is a means of evaluating this probability by comparing it to a null hypothesis, usually a simpler statistical model intended to represent the universe of sequences as a whole, rather than the group of interest. Such scoring leads to two immediate questions: what should the null model be, and what threshold of log-odds score should be deemed a match to the model.

RESULTS

This paper analyses these two issues experimentally. Within the context of the Sequence Alignment and Modeling software suite (SAM), we consider a variety of null models and suitable thresholds. Additionally, we consider HMMer's log-odds scoring and SAM's original Z-scoring method. Among the null model choices, a simple looping null model that emits characters according to the geometric mean of the character probabilities in the columns modeled by the hidden Markov model (HMM) performs well or best across all four discrimination experiments.

Azo polymers for reversible optical storage. 8. The effect of polarity of the azobenzene groups

Poly[4′-[[(2-methacryloyloxy)ethyl]ethylamino]azobenzene] (pMAEA) was prepared. Its reversible optical storage properties were studied and compared with the properties of previously reported poly[4-(2-methacryloyloxy)ethylazobenzene] (pMEA) and poly[4-nitrophenyl-4′-[[2-(methacryloyloxy)ethyl]ethyl-amino]phenyldiazene] (pDR1M). The effect of the dipole moment of the azobenzene moiety on the optical storage properties was studied by comparing the photochemically induced birefringence "writing" and "relaxation" behaviors. The writing and relaxation rates are both in the order pDR1M > pMAEA > pMEA. In addition, pDR1M, which contains donor/acceptor substituents in the azobenzene side chain, exhibits the highest saturation level of optically induced birefringence. The fraction of birefringence conserved after relaxation is lowest for pMEA, which has no donor/acceptor substituents in the azobenzene side chain, and highest for pDR1M. Keywords: polymers, azobenzene type, birefringence, photochemically induced orientation, reversible optical storage.

Oxytocin antisense reduces salt intake in the baroreceptor-denervated rat

Experiments were performed to evaluate the role of central oxytocin (OT) in the inhibition of salt intake produced by sinoartic denervation (SAD). The effect of OT antisense treatment on 24 h intake of 2% NaCl in SAD and sham-operated (SO) rats was determined. PVN injection of unmodified antisense oligodeoxynucleotides (ODNs) to OT mRNA decreased intake of 2% NaCl in SAD, but not SO rats. Salt consumption was 22 +/- 4 ml after the injection of control ODN as compared to 8 +/- 4 ml after the OT antisense injection (P < 0.05). SAD animals also demonstrated an increased plasma OT response to salt loading, an elevation from 3.2 +/- 0.7 to 6.9 +/- 0.8 pg/ml. In contrast, salt ingestion produced no significant change in plasma OT in the SO group. The increased endocrine response in the SADs occurred even though salt intake was lower in this group. There were no group differences in plasma electrolytes or posterior pituitary OT content. Results show that OT antisense specifically inhibits salt intake in the denervated rat, suggesting that the central oxytocinergic axis stimulates sodium drive in this experimental model.