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Biomedical subjects

M C Smith

Publications and source records attributed to M C Smith.

At least 73 records · Page 4Linked to original sources
PubMed1996

Structural comparison of a 15 residue peptide from the V3 loop of HIV-1IIIb and an O-glycosylated analogue.

As part of a program to study the effect of glycosylation on the three-dimensional structures of HIV-1IIIB V3 peptide constructs, we have examined the solution structures of a 15 residue peptide (RIQRGPGRAFVTIGK, P18IIIB)- originally mapped as an epitope recognized by CD8+ Dd class I MHC-restricted murine cytotoxic T-lymphocytes (CTL), and an analogue (P18IIIB-g), O-glycosylated with an alpha-galactosamine on Thr-12, using NMR, circular dichroism and molecular modeling methods. Our studies show that the peptides sample mainly random conformations in aqueous solution near 25 degrees C and become more ordered by the addition of trifluoroethanol. Upon decreasing the temperature to 5 degrees C, a reverse turn is formed around the immunodominant tip (G5-R8). Glycosylation on T12 'tightens' the turn slightly as suggested by NOE and CD analysis. In addition, the sugar has a defined conformation with respect to the peptide backbone and influences the local peptide conformation. These data suggest that simple glycosylation may influence the conformational equilibrium of a V3 peptide which contains a domain critical for antibody recognition and virus neutralization. We also show that the ability of cytotoxic T-lymphocytes (CTL) to lyse tumor cells presenting P18IIIB was completely abrogated by threonine glycosylation.

Amino Acid Sequence↗
PubMed1996

Isolation and sequencing of the rho gene from Streptomyces lividans ZX7 and characterization of the RNA-dependent NTPase activity of the overexpressed protein.

The gene for transcription termination factor Rho was isolated from Streptomyces lividans ZX7. It encoded a 77-kDa polypeptide (Rho 77) with considerable homology to known Rho factors. An atypical hydrophilic region of 228 residues was found within the N-terminal RNA-binding domain. Only Rho from Micrococcus luteus and Mycobacterium leprae (closely related GC-rich Gram-positive bacteria) had an analogous sequence. Rho 77 was overexpressed in Escherichia coli and purified using an N-terminal hexahistidine-tag. Rho 77 displayed a broad RNA-dependent ATPase activity, with poly(C) RNA being no more than 4-fold more effective than poly(A). This contrasts with the ATPase activity of Rho from E. coli which is stimulated primarily by poly(C) RNA. Rho 77 was a general RNA-dependent NTPase, apparent Km values for NTPs were: GTP 0.13 mM, ATP 0.17 mM, UTP 1.1 mM, and CTP >2 mM. Rho 77 poly(C)-dependent ATPase activity was inhibited by heparin, unlike the E. coli Rho. The antibiotic bicyclomycin inhibited the in vitro RNA-dependent ATPase activity of Rho 77, did not inhibit growth of streptomycetes but delayed the development of aerial mycelia. N-terminal deletion analysis to express a truncated form of Rho (Rho 72, 72 kDa) indicated that the first 42 residues of Rho 77 were not essential for RNA-dependent NTPase activity and were not the targets of inhibition by heparin or bicyclomycin.

Adenosine Triphosphatases↗
PubMed1996

Prednisone improves renal function and proteinuria in human immunodeficiency virus-associated nephropathy.

PURPOSE: To determine if prednisone ameliorates the course of human immunodeficiency virus-associated nephropathy (HIV-AN). PATIENTS AND METHODS: Twenty consecutive HIV-infected adults with biopsy-proven HIV-AN (n = 17) or clinical characteristics of HIV-AN (n = 3) with serum creatinine concentrations > 177 mumol/L (2 mg/dL) or proteinuria > 2.0 g/d or both were prospectively evaluated and treated with prednisone at a dose of 60 mg/d for 2 to 11 weeks, followed by a tapering course of prednisone over a 2- to 26-week period. Serum creatinine concentration, 24-hour protein excretion, serum albumin, and steroid-related adverse effects were assessed before and after treatment. RESULTS: Nineteen patients had serum creatinine concentrations > 117 mumol/L (2 mg/dL). Two of them progressed to end stage renal disease (ESRD) in 4 to 5 weeks. In 17 patients serum creatinine levels decreased from 717 +/- 103 mumol/L (8.1 +/- mg/dL) (mean +/- SE) to 262 +/- 31 mumol/L (3.0 +/- 0.4 mg/dL) (P < 0.001). Five patients relapsed after prednisone was discontinued and were retreated. In these 5 the serum creatinine declined from 728 +/- 107 mumol/L (8.2 +/- 1.2 mg/dL) to 344 +/- 47 mumol/L (3.9 +/- 0.5 mg/dL) (P < 0.01) in response to the second course of prednisone. Twelve of 13 tested patients showed a reduction in 24-hour urinary protein excretion with an average decrement from 9.1 +/- 1.8 g/d to 3.2 +/- 0.6 g/d (P < 0.005). Serum albumin increased from 24.4 +/- 3.6 g/L to 29.3 +/- 2.6 g/L (P = NS) in the 11 patients with paired 24-hour urine collections for whom pre- and post-treatment determinations were available. In one non-azotemic patient with nephrotic syndrome, protein excretion declined from 15.2 to 2.2 g/day and the serum albumin increased from 4.0 g/L to 31.0 g/L. The 20 patients have been followed for a median of 44 weeks (range 8 to 107). Eight ultimately required maintenance dialysis. Eleven died from complications of HIV disease 14 to 107 weeks after institution of prednisone; none was receiving prednisone at the time of death. Seven are alive and free from ESRD a median of 25 weeks (range 8 to 81) from the initiation of prednisone therapy. Six patients developed a total of seven serious infections while receiving prednisone, including Mycobacterium avium-complex infection in 2 and CMV retinitis in 3. CONCLUSION: Prednisone improves serum creatinine and proteinuria in a substantial proportion of adults with HIV-AN. Corticosteroid-related side effects are not prohibitive. A prospective, randomized controlled trial is required to confirm these preliminary results.

Adult↗
PubMed1996

Epilepsy.

Diagnosis and management of the epilepsies are routinely performed by primary care physicians. In the United States, only 17% of patients with new-onset epilepsy are examined by neurologic specialists, and even fewer patients employ neurologists for their ongoing care. With the changes dictated by the evolving health care system in the United States, the responsibilities for the treatment of patients with epilepsies by primary care physicians will continue to increase. At the same time, there has been an explosion of new information about the diagnosis, evaluation, natural history, and neurobiologic aspects of epilepsy. New medical and surgical treatments are being introduced with a quickening pace. Finally, the concept that certain epilepsies may be progressive and that early identification and aggressive treatment represent one's best chance for establishing control for these patients has gained widespread confirmation from both clinical and animal model studies. The past standard of care is quickly ending. No longer should a patient or a physician accept only partial seizure control. This monograph attempts to lay the basis for improved understanding of epilepsy so that our patients will be seizure free without side effects and will be able to fully participate in our society.

Aged↗
PubMed1996

Dementia and response to pain in the elderly.

To investigate the effect of dementia on response to pain, 51 community-dwelling, generally healthy, cognitively intact individuals > or = 65 years old and 44 community- or nursing home-dwelling persons > or = 65 years old with varying severity of dementia were studied. Cognitive status was assessed by standardized clinical evaluation and psychometric test performance. The following responses were measured before, during and after a standard venipuncture procedure: heart rate, the amplitude of respiratory sinus arrhythmia (RSA), self-reported anxiety and pain, and videotaped facial expressions. Although RSA did not differentiate procedural phases, in both samples, mean heart rate increased in the preparatory phase and decreased in the venipuncture phase. Independent of age, increasing severity of dementia was associated with blunting of physiologic response as measured by diminished heart rate increase in the preparatory phase and heart rate increase with venipuncture. Dementia significantly interfered with the subjects' ability to respond to direct questions about anxiety and pain. Those who were able to respond were relatively accurate self-assessors: higher anxiety was associated with greater magnitude heart rate responses. Facial expression was increased in demented individuals but it could not be classified by specific emotions. We conclude that dementia influences both the experience and reporting of pain in elderly individuals.

Aged↗
PubMed1996

Spontaneous and posed facial expression in Parkinson's disease.

Spontaneous and posed emotional facial expressions in individuals with Parkinson's disease (PD, n = 12) were compared with those of healthy age-matched controls (n = 12). The intensity and amount of facial expression in PD patients were expected to be reduced for spontaneous but not posed expressions. Emotional stimuli were video clips selected from films, 2-5 min in duration, designed to elicit feelings of happiness, sadness, fear, disgust, or anger. Facial movements were coded using Ekman and Friesen's (1978) Facial Action Coding System (FACS). In addition, participants rated their emotional experience on 9-point Likert scales. The PD group showed significantly less overall facial reactivity than did controls when viewing the films. The predicted Group X Condition (spontaneous vs. posed) interaction effect on smile intensity was found when PD participants with more severe disease were compared with those with milder disease and with controls. In contrast, ratings of emotional experience were similar for both groups. Depression was positively associated with emotion rating but not with measures of facial activity. Spontaneous facial expression appears to be selectively affected in PD, whereas posed expression and emotional experience remain relatively intact.

Aged↗
PubMed1996

Facial expression in adults with Down's syndrome.

The facial expressions of adults with Down's syndrome (DS; n = 15) as they watched happy, sad, and neutral videotapes were compared with those of a healthy age-matched control group (n = 20). Facial movements were analyzed with the Facial Action Coding System (P. E. Ekman & W. V. Friesen, 1978). While watching happy stimuli, the 10 DS adults who were able to appropriately rate their reactions smiled with a cheek raise as frequently as control adults, suggesting that the expression of positive affect in these individuals is normal. Contrary to predictions, however, the DS group exhibited fewer smiles without cheek raises than did control adults and were more likely not to smile. Neither group showed prototypic sad facial expressions in response to sad stimuli. Independent of emotion, DS participants made more facial movements, including more tongue shows, than did control participants. Differences in facial expression in DS adults may confuse others' interpretations of their emotional responses and may be important for understanding the development of abnormal emotional processes.

Adult↗
PubMed1996

Characterization of a late promoter from the Streptomyces temperate phage phi C31.

An operon expressed late in the lytic cycle of the Streptomyces temperate phage phi C31 was shown to be transcribed from an inducible promoter, phi lp (phage late promoter), which resembled the previously reported early promoters. mRNAs initiated at phi lp were processed at the 3' end (and possibly also the 5' end) of a tRNA(Thr)-like sequence, resulting in leaderless polycistronic mRNAs.

Bacteriophages↗
PubMed1996

Getting angry at peers: associations with linking of the provocateur.

We examined how preschoolers coped with anger in interactions with well liked and not well liked peers. The free-play interactions of preschool-aged children (M age = 66.27 months) were observed for 6 months. The frequency, causes, and intensity of children's anger, as well as their anger-related reactions, were compared for incidents provoked by peers who were "really liked" to those provoked by peers who were liked only " a little bit." Although there were no differences in the intensity of anger provocations by well liked and not well liked provocateurs, children's responses to provocations by well liked peers were more controlled than was the case for anger provoked by peers who were not well liked. In general, boys were more responsive to how they felt about the provocateur than were girls. These findings suggest that anger episodes with well liked children were less stressful than those with peers who were not well liked.

Adaptation, Psychological↗
PubMed1996

Hypersensitivity to rapamycin of BJAB B lymphoblastoid cells.

Proliferation of the BJAB B-lymphoblastoid cell line was rapidly and almost completely suppressed by picomolar concentrations of the immunosuppressive macrolide rapamycin (50% inhibitory concentration 10-20 pM for cells reactivated from stationary phase). This cell line was considerably more sensitive to rapamycin than any other B-lymphoblastoid cell line tested, the Jurkat T-cell line or the HL60 promyelocytic cell line. BJAB cell proliferation was not affected by the related immunosuppressive macrolides FK506 or L-685,818, which bind to the immunophilin FKBP12 competitively with rapamycin and also inhibit its peptidylprolyl cis-trans isomerase activity. Excess FK506 or L-685,818 added simultaneously competitively antagonized rapamycin's anti-proliferative action. Levels of FKBP12 and uptake of rapamycin from the culture medium were also normal in BJAB cells. The hypersensitivity to rapamycin of BJAB cells thus reflects an unusual dependence on the intracellular signalling system targeted by the rapamycin-FKBP12 complex, and may provide a model system for elucidating the role played by this pathway in lymphocyte activation. The proliferation of BJAB cells reactivated from stationary phase can also be used as the basis for a highly sensitive bioassay for the presence of rapamycin in culture media or other biological fluids.

B-Lymphocytes↗
PubMed1995

Fragmentation of the neuronal cytoskeleton in the Lewy body variant of Alzheimer's disease.

We studied neuronal alterations in the Lewy body variant of Alzheimer's disease (LBV) with a monoclonal antibody (SMI32) against non-phosphorylated neurofilament proteins, and compared them with the alterations found in pure Alzheimer's disease (AD). A characteristic granular and fragmented appearance of SMI32-immunolabeled pyramidal neurons in layers 3 and 5 of the neocortex occurred in 78% of the LBV cases and was not found in the pure AD cases. Lewy bodies (LBs) in pyramidal neurons in layers 5 and 6 immunoreacted with SMI32 in 44% of the LBV cases. These alterations may be associated with the cognitive deficits found in LBV and are suggestive of an underlying, widespread pathology that includes both disruption of the neurofilamentous cytoskeleton and formation of LBs.

Aged↗
PubMed1995

Rho-independent terminators without 3' poly-U tails from the early region of actinophage øC31.

Previous work has identified three intergenic regions from the early region of actinophage øC31 where transcription was either terminated or the mRNA was processed. Here we show using in vivo and in vitro approaches that these regions contain rho-independent terminators designated eta, etb and etc. Transcripts through eta-c would be expected to form stable RNA stem-loops but would lack poly-U tails. Eta-c contained part or all of the conserved sequences 5' AGCCCC and 5' GGGGCTT. A Streptomyces 'terminator probe' vector, pUGT1, was constructed and used to assay the efficiency of termination of transcription by eta-c from the thiostrepton-inducible tipA promoter by measuring the expression of a downstream reporter gene (aphII). In pUGT1 etb was at best a minor terminator in vivo whilst eta and etc exhibited strong termination activity. In vitro termination was assayed using templates containing a synthetic promoter recognised by E.coli RNA polymerase and fragments containing eta-c inserted downstream. All three terminators stimulated the formation of 3' ends in the promoter-distal arm of the inverted repeats with efficiencies eta > etc > etb. As all three terminators either overlap with or lie close to sequences which interact with phage repressor proteins (conserved inverted repeats, CIRs) and these can potentially form stem-loop structures in RNA, the effect of CIRs on termination was also investigated. Termination at etb was unaffected by the presence or absence on the transcription template of CIR3. CIR4 forms the central 17 bp of etc and a 37 nt deletion which eliminated this stem-loop abolished termination in vivo and in vitro. Eta was investigated using an antisense oligonucleotide interference assay; an oligo designed to bind the 5' arm of eta inhibited termination whilst an oligo antisense to CIR5 was ineffective and an oligo targeted further upstream enhanced termination. Taken together these data show that eta-c are intrinsic, rho-independent terminators of varying efficiencies despite the absence of a poly-U tail.

Bacteriophages↗
PubMed1995

Tailored anterior temporal lobectomy. Relation between extent of resection of mesial structures and postsurgical seizure outcome.

OBJECTIVE: The purpose of this study was to assess the relationship between the extent of resection of mesial temporal structures and postsurgical seizure outcome in a group of patients who had undergone a tailored anterior temporal lobectomy. METHODS: Twenty-four patients with unilateral interictal and ictal foci restricted to anterior/mesial temporal regions underwent resection of mesial and temporal lateral structures, the extent of which was tailored by intraoperative electrocorticographic findings and functional mapping of eloquent cortex. The extent of resection was determined with postoperative magnetic resonance imaging scans, using a semiquantitative method, based on a 20-compartment model of the temporal lobe. The magnetic resonance imaging scans were rated by three investigators blinded to seizure outcome. Follow-up period ranged between 18 months and 5 years. RESULTS: Amygdala and hippocampus were spared in six patients; nine patients had a partial to total resection of amygdala, eight patients had a resection of amygdala and the anterior third of the hippocampus, and one patient underwent resection of amygdala and anterior two thirds of hippocampus. Twenty-one of the 24 patients were seizure free (Engel's class I) and three had rare seizures (Engel's class II). Among these three patients, one had a resection of amygdala; one had resection of amygdala and anterior third of hippocampus; while in the third patient, mesial structures were spared. CONCLUSION: These data suggest that in patients with an anterotemporal seizure focus, the sparing or limited resection of amygdala and/or hippocampus is not necessarily associated with a poor seizure outcome, as had been previously suggested, provided that the decision not to resect is based on the absence of epileptiform activity during intraoperative electrocorticography or during recordings with depth electrodes.

Adolescent↗