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S Roberts

Publications and source records attributed to S Roberts.

At least 181 records · Page 10Linked to original sources
PubMed1995

TFIIIC determines RNA polymerase III specificity at the TATA-containing yeast U6 promoter.

The gene encoding yeast U6 snRNA that is transcribed by RNA polymerase III (Pol III) contains both a TATA box upstream of the transcription start site and a downstream binding site for the factor TFIIIC. This juxtaposition of elements typical of both Pol II- and Pol III-transcribed genes raises the question of how polymerase specificity is determined. The upstream U6 promoter containing the TATA box and transcription start site was shown previously to be transcribed by Pol III in vitro. We therefore tested whether the upstream promoter of yeast U6 encodes Pol III specificity. One model is that polymerase specificity is conferred by the homologous Pol II and Pol III transcription factors TFIIB and BRF1. However, we found no specificity in the binding of BRF1 or TFIIB to TATA-containing promoters of genes specifically transcribed by Pol III or Pol II. Yeast strains deficient for Pol II or Pol III transcription were employed to examine U6 polymerase specificity in vivo. We find that the U6 upstream promoter is Pol II-specific in vivo and is converted to Pol III specificity by TFIIIC. Thus, preferential recruitment of TFIIIB by TFIIIC probably excludes the Pol II general factors and promotes Pol III transcription, thereby determining polymerase specificity.

Base Sequence↗
PubMed1995

The quaternary structure of the adenovirus 12 early region 1B 54K protein.

The quaternary structure of the adenovirus early region 1B 54K protein has been examined under denaturing and nondenaturing conditions. In the presence of SDS the protein has a strong tendency to form disulfide-linked high-molecular-weight polymers. Under nondenaturing, but reducing, conditions the in vitro-translated 54K polypeptide forms oligomers (probably tetramers) of molecular weight approximately 2 x 10(5). After subcellular fractionation of Ad12 early region 1-transformed cells, the 54K E1B protein present in the cytoplasm had a molecular weight similar to that determined for the in vitro-translated material. However, two populations of the viral protein could be distinguished in the nucleus-one of a size similar to that seen in the cytoplasm and the other of appreciably higher molecular weight (approximately 2 x 10(6)). No difference in migration pattern was observed after treatment of the nuclear extract with DNase I or RNase. A proportion of the Ad12 E1B 54K protein in both the high- and the low-molecular-weight populations in the nucleus was found to form a complex with p53, and it is therefore concluded that the very high molecular weight derives from interaction with an, as yet, unidentified component.

Adenovirus E1B Proteins↗
PubMed1995

The maternal-fetal transfer of bisheteroypiperazine (U-87201-E) in the ex vivo human placenta.

OBJECTIVE: The purpose of this study was to elucidate the maternal-fetal transfer of bisheteroypiperazine (U-87201-E), a nonnucleoside reverse transcriptase inhibitor of human immunodeficiency virus-1. STUDY DESIGN: Placentas from normal term deliveries were used in this study to determine the maternal-fetal transfer of bisheteroypiperazine. The studies were conducted at several concentrations with the circulation either open-open or closed-closed. RESULTS: In this study we determined that the clearance index of bisheteroypiperazine was 0.72 +/- 0.17 at maternal concentrations of 1.0 and 20.0 micrograms/ml. This is at least twice the clearance index of 3'-azido-2',3'-dideoxythymidine and more than five times greater than that of 2',3'-dideoxyinosine. CONCLUSIONS: Bisheteroypiperazine crosses the maternal-fetal membranes by simple diffusion, in some instances almost equivalent to the reference compound antipyrine. Placental tissue concentrations were equivalent at all maternal concentrations, suggesting saturation. This high rate of maternal-fetal transfer suggests that it may be an effective prophylactic drug for fetuses of human immunodeficiency virus-infected mothers.

Female↗
PubMed1995

Ex vivo human placental transfer of human immunodeficiency virus-1 p24 antigen.

OBJECTIVE: Our purpose was to determine whether human immunodeficiency virus-1 p24 antigen crosses the human placenta and, if so, to determine its clearance index relative to antipyrine. STUDY DESIGN: Eight term human placentas from uncomplicated vaginal or cesarean section deliveries were studied by ex vivo placental perfusion to determine the incidence and concentration required to obtain passage of p24 antigen into the fetal circulation. The concentration of p24 antigen was determined by antigen-capture enzyme immunoassay. RESULTS: The passage of p24 antigen into the fetal circulation was observed in three of five placentas studied when the p24 antigen concentration in the maternal circulation was 2942.8 +/- 401 pg/ml. When the p24 concentration in the maternal circulation was raised approximately fourfold to 14506 +/- 4124 pg/ml, p24 antigen passed to the fetal circulation in two of three placentas and in three of three placentas in the closed perfusion system. CONCLUSIONS: p24 antigen crossed the human placenta to the fetal circulation in what appears to be a concentration-dependent manner.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Development and degeneration of the intervertebral discs.

The intervertebral discs undergo profound changes in structure and composition during development and aging. They also degenerate much earlier than other cartilaginous tissues, and in severe cases may lose function completely. The reasons for this early degeneration are unknown, but external factors, such as mechanical overload on the spine, or smoking, may be involved. However, recent work has revived interest in the importance of genetic and developmental influences on the intervertebral discs.

Aging↗
PubMed1995

Calcium influx, fertilisation potential and egg activation in Fucus serratus.

Fertilisation in the marine alga Fucus serratus is accompanied by increased influx of Ca2+ from the external medium. The onset of this increase, monitored with the Mn2+ fluorescence quench technique, corresponded with the depolarisation phase of the fertilisation potential. External Ca2+ was necessary for the onset of the fertilisation potential and the early activation events, including cell wall exocytosis. Removal of Ca2+ from, or addition of Sr2+ to, the external medium during the fertilisation potential reduced the magnitude of the depolarisation and prolonged its duration. While fertilisation potentials could not be elicited in the presence of 0.1 mM Ca2+, addition of Ba2+ in the presence of 0.1 mM Ca2+ allowed normal fertilisation potential and egg activation. Microinjection of ryanodine or cyclic guanosine 5' -monophosphate (cGMP) did not induce cytoplasmic Ca2+ elevation or egg activation. Inositol 1,4,5-triphosphate [Ins(1,4,5)P3] produced a transient elevation of cytoplasmic Ca2+, monitored using ratio photometry, but did not cause cell wall exocytosis except at the site of microinjection. The results demonstrate an essential role for Ca2+ influx during Fucus egg activation. The relative importance of influx and intracellular Ca2+ release in Fucus egg activation is discussed.

Calcium↗
PubMed1995

Neurodevelopmental outcome in very low birthweight infants with necrotizing enterocolitis requiring surgery.

OBJECTIVE: To assess the effect of necrotizing enterocolitis (NEC) on neurodevelopmental outcome. METHODOLOGY: Neurodevelopmental outcome of 20 very low birthweight (VLBW) infants who developed NEC requiring surgery was compared with 40 matched infants controlled for gestation, birthweight, and year of admission. Twenty-nine VLBW infants who developed NEC and did not require surgery were also compared. RESULTS: Infants with NEC needing surgery were of 26 +/- 2 weeks gestation and weighted 892 +/- 192 g at birth. Infants with NEC managed medically were of higher gestation (27 +/- 2 weeks) but similar birthweights. More infants with NEC requiring surgery required inotropic support. At follow up, NEC surgery infants had a significantly higher incidence of developmental morbidity. 11 of 20 compared with 11 of 40 matched controls (Fisher's exact test P = 0.0493), and six of 29 infants with NEC managed medically (Fisher's exact test P = 0.0174). CONCLUSIONS: These findings stress the importance for close follow up for neurodevelopmental sequelae in VLBW infants who have had NEC requiring surgery.

Blindness↗
PubMed1995

Chronic generalized obliterative arteriopathy in cattle: a sequel to sheep-associated malignant catarrhal fever.

Malignant catarrhal fever (MCF) in cattle is generally associated with a short clinical course and a high case fatality rate (90-95%). The lesions in cattle that survive acute MCF for a prolonged period or appear to recover have not been documented. In a naturally occurring outbreak of MCF in a herd of beef cattle in Wyoming, 7 of 84 yearling heifers (8.3% of replacement herd) and 2 of 230 cows (0.9% of cow herd) developed clinical signs of pyrexia, mucopurulent discharge, bilateral keratitis, and weight loss following contact with ewes that had lambed 34-62 days earlier. Six of 9 affected cattle were examined postmortem following clinical signs (CS) that developed 2-150 days earlier. Three cattle with CS for < or = 39 days had lesions of regional lymphadenopathy and widespread severe segmental lymphoid arteritis-phlebitis that were typical of acute MCF, and proliferative intimal lesions were present in a small proportion of arteries at days 20 and 39 of CS. By contrast, 3 cattle that survived to 90, 105, and 150 days after clinical onset had distinctive arterial lesions in multiple organs, characterized by proliferative concentric fibrointimal plaques, disrupted inner elastic lamina, focally atrophic tunica media, and vasculitis of variable severity. Immunohistochemical and ultrastructural examination of intimal plaques identified the predominant cellular component to be smooth muscle cells with a contractile phenotype. No viral structures were seen. Serologic studies, using a competitive inhibition enzyme-linked immunosorbent assay (CI-ELISA) that detects antibody to an epitope broadly conserved among isolates of the MCF virus, found that 2 chronically affected cattle were serologically positive between days 42 and 100 of CS, with seroconversion in 1 animal between days 52 and 73 of CS. Seroprevalence was 7.9% in the 76 remaining healthy animals of the replacement heifer herd and 40% (75% in adult sheep and 4% in lambs) in the in-contact sheep flock 77 days after onset of CS in the index case. This episode suggests that, in addition to the common and well recognized acute form of MCF in cattle, this viral infection encompasses a disease spectrum that includes chronic disease and partial to "complete" clinical recovery, and in recovered animals chronic obliterative arteriopathy is the preeminent lesion.

Animals↗
PubMed1995

Computer-assisted fabrication of orthodontic appliances: considering the possibilities.

The authors describe a computer-controlled system that can partially automate the fabrication of maxillary orthodontic appliances. The system can be programmed to deposit and cure the acrylic portion of these appliances. Using this new process, the operator places the orthodontic wires and expansion screws on the surface of the dental cast, secures the cast onto the machine and describes the desired shape of the appliance via graphical user interface. The machine then applies and cures the acrylic to form the finished appliance. Only minimal grinding and buffing is required.

Acrylic Resins↗
PubMed1995

Helical CT of the liver: clinical application of an automated computer technique, SmartPrep, for obtaining images with optimal contrast enhancement.

OBJECTIVES: The purpose of this study was to evaluate an automated computer technique (SmartPrep) for achieving a consistently high level of contrast enhancement in the liver with helical CT. The technique compensates for variability between patients by indicating graphically the time at which scanning should be initiated to reach a desired level of hepatic enhancement. MATERIALS AND METHODS: One hundred nine consecutive patients undergoing helical CT of the abdomen were randomly evaluated, using either a standard 70-sec delay from the start of the injection of contrast material to scanning or a newly developed, commercially available automated technique, SmartPrep. A series of multiple low-dose scans was performed until an arbitrary threshold of hepatic enhancement (50 H) over baseline was achieved. Three regions of interest (ROIs) were imaged on a baseline scan and on contrast-enhanced scans at the upper, mid, and lower liver. Average hepatic enhancement and the standard deviation over baseline was calculated for each group at all anatomic levels. For the SmartPrep group, the range of time between scan initiation and onset of scanning was calculated. RESULTS: The mean hepatic enhancement for the control group (n = 56) was 59.8 +/- 20.1 H, which differed significantly (p = .0002) from that for the SmartPrep group (n = 53), which was 71.6 +/- 15.2 H. Comparison of the variability between the two groups' enhancement levels was also significant (p = .02). The range of delay times for the SmartPrep group was 48-86 sec. In two additional cases, abnormal graphically displayed enhancement curves were the first indication of an improper injection. CONCLUSION: Use of SmartPrep yields a greater and more consistent level of hepatic enhancement from patient to patient than does use of a conventional fixed delay time. The ability to scan more efficiently to achieve greater hepatic enhancement using SmartPrep has significant implications for potential contrast cost savings.

Diagnosis, Computer-Assisted↗
PubMed1995

Analyzing Behavior State and Learning Environments: application in instructional settings.

An evaluation of the effects of the ABLE (Analyzing Behavior State and Learning Environments) model was presented. Eight teachers received training on observing behavior state and relevant environmental variables; analyzing potential effects of nutrition and medications; identifying strategies for individual students; and participating in a process to generate classroom-based intervention strategies based on their observations. Results showed that teachers were able to reliably implement the model, which produced significant increases in occurrences of the preferred alert and active states and significant decreases in nonpreferred states, such as sleep, drowse, daze, and crying/agitated. Additional findings indicated that the teachers were satisfied with the training procedures and found the model to be relevant and appropriate for students with profound mental retardation. Case studies were briefly presented.

Adolescent↗
PubMed1995

Replication and extended analysis of behavior state, environmental events, and related variables among individuals with profound disabilities.

Knowledge from previous studies pertaining to state behavior of individuals with profound and multiple disabilities and its relation to other environmental and physiological variables was replicated and extended. Behavior state and environmental data were collected over a 5-hour period for most of 66 students with profound disabilities from 21 educational settings. Results showed general consistency in state patterns and profile groupings with previous investigations, a strong relation between different state profiles and measures of development, and consistency of state patterns across CA levels. Transitional probabilities and z scores were used to confirm changes in state behavior of half of the subjects following primarily adult interactions. Results were discussed in relation to theoretical implications and intervention recommendations.

Activities of Daily Living↗
PubMed1994

Human papillomavirus type 1 E4 protein is a zinc-binding protein.

Study of the human papillomavirus (HPV) E4 gene product has focused largely on HPV type 1 (HPV 1) primarily because of the large quantities of protein that can be purified from HPV 1-induced warts. We have extended the characterization of the HPV 1 E4 protein and, in this study, have shown that protein purified from clinical material and a heterologous expression system contains the divalent metal ion zinc. Furthermore, using a [65Zn]Cl2 dot-blot assay, we have shown that this binding is specific for zinc and those divalent cations that are known to structurally substitute zinc in metalloproteins. Mutational analysis has demonstrated that histidine amino acids (residues 56, 86, and 121), but not the cysteine residue (115), are essential for the zinc-binding activity of the E4 protein. Two assayable functions of E4 are dimerization and the formation of E4/cytokeratin structures in cultured cells; however, neither activity is abrogated by the loss of zinc binding.

Cloning, Molecular↗