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Biomedical subjects

R L Adams

Publications and source records attributed to R L Adams.

At least 37 records · Page 2Linked to original sources
PubMed1997

Cross-validation of predicted Wechsler Memory Scale-Revised scores in a normative sample of 25- to 34-year-old patients.

Equations for prorating Wechsler Memory Scale-Revised General Memory (GM) and Delayed Recall (DR) index scores ([Woodard and Axelrod, 1995]) were confirmed in the [Mittenberg et al. (1992)] normative WMS-R sample of 50 subjects between the ages of 25 and 34, and confirmed in a separate clinical sample of 30 patients with closed head injury who were age, education, and gender matched with 30 subjects from that normative sample. Predicted GM and DR index scores fell within 6 points of the obtained scores for 98% of the [Mittenberg et al. (1992)] sample and 93% to 100% of the matched head injury and normative samples, despite statistically significant differences between these groups in obtained GM, DR, and percent retention of LM I and II and VR I and II. Six points is well within the standard error of measurement of these index scores. These findings confirm the earlier cross-validation results reported by [Axelrod et al. (1996)] in a mixed sample of traumatic brain injury and other neurological insult, and suggest that this method of estimating weighted score sums for WMS-R General Memory and Delayed Recall indices may be safely used in normative samples of patients in this age range as well as neurologically compromised patients without significantly impacting index score accuracy.

Journal Article↗
PubMed1996

Spreading of methylation along DNA.

Mouse DNA methyltransferase is able to catalyse the transfer of a methyl group to certain CG-containing single-stranded oligonucleotides. The presence of a methylcytosine is required for efficient transfer. This methylcytosine may or may not be on the same oligonucleotide as that containing the accepting CG dinucleotide. When the accepting CG dinucleotide forms part of an unmethylated CG dinucleotide pair, its accepting activity is dramatically reduced. This provides the potential for methylation to spread along the DNA when it is rendered single-stranded at replication. It could also help to maintain fully methylated CG islands and asymmetrically methylated sites.

Animals↗
PubMed1996

Photothermal effects on murine mammary tumors using indocyanine green and an 808-nm diode laser: an in vivo efficacy study.

Murine mammary tumors were treated using indocyanine green and an 808 nm diode laser, and the in vivo chromophore-enhanced photothermal effects on the tumor burden and on tumor rat survival were investigated. The power of the laser was selected in the range of 5-10 W, and irradiation duration 3-5 min. One percent aqueous indocyanine green solution in a volume of 100-200 microliters was administered in situ, either acutely or 24 h prior to the treatment. The photothermal interaction was apparent under all our treatment conditions with a well-defined spatial containment in this study and the tumor growth was slowed after treatment. The post-treatment observation showed tumor recurrence and metastasis; no long-term survival was achieved with the single application of laser in conjunction with indocyanine green. Our results pose a question on the efficacy of the photothermal interaction even though tumor cell destruction can be achieved in a large and controlled scale. However, this highly selective photothermal impact on the tumor tissue did suggest that this method be applied repeatedly to be more effective and be used as the precursor of other modalities, such as chemotherapy, radiation therapy, immunotherapy, and surgery.

Animals↗
PubMed1996

Modal profiles for the Halstead-Reitan Neuropsychological Battery.

Modal profile analysis was used to cluster subjects on 11 scores from the Halstead-Reitan Neuropsychological Battery. The final analysis produced 18 modal profile types, of which 12 were replicated in multiple samples of subjects with differing clinical diagnoses. Subjects who had been assigned to modal types according to their correlations with the modal profiles were more similar to the centroid of their assigned groups than to the centroids of all other groups. Assigned subjects were eight times more likely to belong to their assigned groups than to any of the other groups. Fifty-four percent of subjects were assigned to a modal profile group according to the adopted similarity rule. Discussion includes a comparison of the present typology with a similar typology of Luria-Nebraska Neuropsychological Battery profiles.

Journal Article↗
PubMed1995

DNA binding and methyl transfer catalysed by mouse DNA methyltransferase.

By using a purified fraction of mouse DNA methyltransferase we have shown, by gel-retardation analysis, that the enzyme forms a low-affinity complex preferentially with hemimethylated DNA; the complexes formed with unmethylated or with fully methylated DNA are of even lower affinity, and only very weak interaction occurs with DNA lacking CG dinucleotides. Interaction is inhibited by N-ethylmaleimide. Methyl transfer from S-adenosyl-methionine is associated with the release of the fully methylated product from the complex. Complexes formed with the intact enzyme are extremely large, but limited trypsin treatment allows a major complex to enter the gel. DNA binding is not inhibited by this limited proteolysis of the native enzyme.

Animals↗
PubMed1995

Chromophore-enhanced in vivo tumor cell destruction using an 808-nm diode laser.

Rat mammary tumors were treated using an 808-nm diode laser in a power range of 3-15 W. Photothermolysis was selectively enhanced by the chromophore indocyanine green (ICG), which has an absorption peak corresponding to the laser wavelength. ICG, injected into neoplastic tissues 24 h before laser exposure, was retained in sufficient quantity to produce a strong photothermal reaction. With appropriate laser power and adequate irradiation duration, laser energy could inflict severe photothermal damage to the entire targeted tumor tissue while leaving the skin and other interdicted tissue undamaged. Higher laser powers (10-15 W) produced more surface damage that limited light transmission and as a result gave rise to reduced regions of thermal destruction. Post-treatment observation revealed the survival of numerous tumor cells. This finding questions the long term efficacy of the photothermal effect of a single treatment using the combination of the ICG and the diode laser, particularly in the absence of other modalities.

Animals↗
PubMed1995

CG and CNG methyltransferases in plants.

We have purified two distinct DNA methyltransferases from pea shoot tips and analysed their sequence specificity using synthetic oligodeoxyribonucleotide substrates and chemical sequencing methods. One methylates only CG target sequences, whereas the other methylates only CAG or CTG target sequences. We have found no evidence for methylation of the 5' cytosine in CCG target sequences either in vivo or in vitro. Using amino-acid sequence data, PCR-amplified fragments from conserved sequences and heterologous probes, we have isolated several cDNA clones that react with mRNA molecules of different sizes.

Base Sequence↗
PubMed1995

The effect of histone H1 and DNA methylation on transcription.

We have previously shown that DNA methylation acts as a focus for the formation of inactive chromatin in vivo. We have investigated the mechanism further by in vitro transcription of a template containing two tRNA genes and an extensive (G+C)-rich sequence characteristic of a CpG island. The extent of transcription from the unmethylated or fully methylated template was assayed in the presence of varied levels of histone H1. The transcriptional activity of both templates was inhibited by increasing amounts of histone H1, although inhibition with the methylated template occurs at a lower H1:DNA ratio. The H1c variant shows the greatest preferential inhibition of the methylated template. We demonstrated that histone H1 complexed to DNA is one of the factors that inhibits transcription by preventing the formation of initiation complexes, particularly on methylated template, rather than the formation of disordered H1.DNA aggregates.

Ammonium Sulfate↗
PubMed1995

Chromophore-enhanced laser-tumor tissue photothermal interaction using an 808-nm diode laser.

A diode laser was used to irradiate tumor tissue, with indocyanine green as the chromophore. The 808-nm wavelength radiation falls within the absorption peak of the chromophore (about 780 nm). The preliminary results in this report revealed clear and significant coupling of this laser and indocyanine green in laser-tissue photothermal interaction. The chromophore targeted tissue showed laser damage while peripheral tissues remained intact. Without the chromophore, this laser inflicted no apparent tissue damage in the non-contact mode with irradiance up to 1755 J/cm2.

Animals↗
PubMed1995

Eukaryotic DNA methyltransferases--structure and function.

Methylation of DNA plays an important role in the control of gene expression in higher eukaryotes. This is largely achieved by the packaging of methylated DNA into chromatin structures that are inaccessible to transcription factors and other proteins. Methylation involves the addition of a methyl group to the 5-position of the cytosine base in DNA, a reaction catalysed by a DNA (cytosine-5) methyltransferase. This reaction occurs in nuclear replication foci where the chromatin structure is loosened for replication, thereby allowing access to methyltransferases. Partly as a result of their recognising the presence of a methylcytosine on the parental strand following replication, these large enzymes are able to maintain the distribution of methyl groups along the DNA of somatic cells and, thereby, maintain tissue-specific patterns of gene expression.

Animals↗
PubMed1995

Distinct CG and CNG DNA methyltransferases in Pisum sativum.

DNA methyltransferase activity, present in low salt extracts of nuclei from young pea shoot apices, has been fractionated into two different species by assaying with model substrates. The CG methyltransferase (an unstable enzyme believed to be of 140 kDa) methylates cytosine only in oligonucleotides with CG and Cl dinucleotide targets while an enzyme of 110 kDa (the CNG methyltransferase) methylates the cytosines in 5'-CAG-3' and 5'-CTG-3' target sequences, especially when hemimethylated, but not in 5'-CCG-3' nor in 5'-CGG-3' target sequences present in oligonucleotides.

Base Sequence↗
PubMed1995

A comparison of indices of premorbid intelligence in clinical populations.

Estimation of premorbid intelligence using the regression formula developed by Barona et al. (1984) was compared with prorated IQ's based on the higher of the Vocabulary or Picture Completion subtests from the WAIS-R. Actual and predicted premorbid IQ's of 50 brain-damaged patients were compared to those of 35 non-brain-damaged patient controls equated on age and education. For both groups, the Barona et al. (1984) formula produced mean IQ's close to 100, though greatly restricted the range. The prorated IQ's tended to be over-estimated in the patient control group, but not the brain-damaged group. Compared with the regression based formula, the distribution of these prorated IQ's was more consistent with the WAIS-R standardization sample.

Journal Article↗
PubMed1995

Interpretive significance of variability of performance on neuropsychological tests.

The interpretive significance of variability of performance on neuropsychological measures was investigated in groups of brain-damaged and non-brain-damaged subjects. The 39 brain-damaged subjects were matched on Full Scale IQ and age with 39 non-brain-damages subjects. The two groups failed to differ on a measure of level of performance, but did differ on variability of performance. The results were interpreted as providing support for the clinical utility of measures of variability of performance and indicating the need for additional investigation of such measures.

Journal Article↗
PubMed1994

Preserved cognitive skills in dementia of the Alzheimer type.

OBJECTIVE: To describe preserved cognitive skills in patients with dementia. DESIGN: Case series. SETTING: Community clinic. PATIENTS: Five patients who met National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria for probable Alzheimer's disease and were claimed to retain a cognitive skill. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Standard neuropsychological tests and individualized measures of patient's skilled behaviors. For patients who remained skilled at games, performance was compared with that of normal controls in direct competition. For the patient-trombonist, raters compared premorbid and postmorbid recordings of his play. RESULTS: One patient continued to play the trombone in a Dixieland band, although he could not name well-known numbers that he played. Another continued to solve adult jigsaw puzzles. A third patient retained skill at canasta, the fourth at dominoes. The fifth patient remained a skillful contract bridge player, although he could not name the suits or articulate simple bidding rules. Four patients had impaired performance on standard anterograde and remote memory and naming tests but performed normally on pursuit rotor and letter fluency tests. Mini-Mental State Examination scores for these patients ranged from 10 to 22. One patient refused neuropsychological testing but displayed his skill. CONCLUSIONS: Together with previous studies of preserved piano playing or painting skills, our findings indicate that a broad range of complex cognitive abilities may be preserved in patients with dementia of the Alzheimer type who cannot perform simpler actions.

Aged↗