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Biomedical subjects

R C Martin

Publications and source records attributed to R C Martin.

At least 55 records · Page 3Linked to original sources
PubMed1998

Individual memory change after anterior temporal lobectomy: a base rate analysis using regression-based outcome methodology.

PURPOSE: To characterize patterns of base rate change on measures of verbal and visual memory after anterior temporal lobectomy (ATL) using a newly developed regression-based outcome methodology that accounts for effects of practice and regression towards the mean, and to comment on the predictive utility of baseline memory measures on postoperative memory outcome. METHODS: Memory change was operationalized using regression-based change norms in a group of left (n = 53) and right (n = 48) ATL patients. All patients were administered tests of episodic verbal (prose recall, list learning) and visual (figure reproduction) memory, and semantic memory before and after ATL. RESULTS: ATL patients displayed a wide range of memory outcome across verbal and visual memory domains. Significant performance declines were noted for 25-50% of left ATL patients on verbal semantic and episodic memory tasks, while one-third of right ATL patients displayed significant declines in immediate and delayed episodic prose recall. Significant performance improvement was noted in an additional one-third of right ATL patients on delayed prose recall. Base rate change was similar between the two ATL groups across immediate and delayed visual memory. Approximately one-fourth of all patients displayed clinically meaningful losses on the visual memory task following surgery. Robust relationships between preoperative memory measures and nonstandardized change scores were attenuated or reversed using standardized memory outcome techniques. CONCLUSIONS: Our results demonstrated substantial group variability in memory outcome for ATL patients. These results extend previous research by incorporating known effects of practice and regression to the mean when addressing meaningful neuropsychological change following epilepsy surgery. Our findings also suggest that future neuropsychological outcome studies should take steps towards controlling for regression-to-the-mean before drawing predictive conclusions.

Adult↗
PubMed1998

Contribution of neuropsychological data to the prediction of temporal lobe epilepsy surgery outcome.

PURPOSE: We empirically examined the contribution of neuropsychological data to the prediction of postoperative seizure control relative to base rate information in an existing series of patients undergoing anterior temporal lobectomy (ATL). METHODS: A discriminant function predicting surgery outcome (seizure-free vs. non-seizure-free) was computed separately for samples of patients with left (n = 79) and right (n = 62) temporal lobectomy (LATL, RATL). Predictor variables included 14 measures tapping five neurocognitive domains. The predicted base rates were compared with the actual base rates in the two samples. Finally, overall predictive accuracy was examined in optimal versus suboptimal ATL patients. RESULTS: The base rate of seizure freedom in the LATL group was 74.70%; that in the RATL group was 66.10%. The predictive function for the LATL group achieved a hit rate of 80.00% and a positive predictive power of 92.11%. The function for the RATL group achieved a hit rate of 83.33% and a positive predictive power (PPP) of 89.66%. The overall predictive accuracy for the optimal group was only 55%, but that in the suboptimal group was 72%. CONCLUSIONS: Neuropsychological data used in a multivariate statistical fashion may be able to offer an incremental increase in the prediction of postoperative seizure freedom relative to existing base rates of surgery success in patients with ATL epilepsy. The use of neuropsychological data may be of greatest predictive value in a population of ATL candidates with suboptimal findings with a lower base rate of postoperative seizure freedom, but may actually reduce predictive accuracy in a group of ATL candidates from an optimal population with an already high base rate of surgical success.

Adult↗
PubMed1998

Mobile mammography screening: the James Graham Brown Cancer Center three year experience. Implications for public and professional education.

OBJECTIVE: Review the mobile mammography screening experience at the James Graham Brown Cancer Center during a 3 year interval. METHODS: Collect and analyze demographic and outcome data on the screened population. RESULTS: 4,864 women underwent two-view mammograms. One third of the mammograms were performed in women over 50 years of age. 232 mammograms were carried out per cancer detected. The number of mammograms per cancer detected was 2.5 times higher and the number of biopsies per cancer detected was 2.8 times higher in women under 50 years of age. Two thirds of the cancers detected were in the over 50 age group which represents one third of the study population. CONCLUSIONS: In this study, mammographic screening for breast cancer was more cost effective because a higher yield of cancers detected was obtained with fewer mammograms and fewer breast biopsies in women over 50 years of age, compared to women under 50 years. Resolving the question of the cost effectiveness of screening women aged 40 to 49, will require a large randomized prospective trial. In the near term, rather than to dwell on this issue, we would propose that this study suggests the need for greater emphasis in both public and professional education on breast cancer detection directed to women over 50 years of age.

Adult↗
PubMed1998

Multiple interference effects in short-term recognition memory.

Five experiments, using a probe recognition procedure, examined the codes involved in short-term memory. Interference effects were obtained for probes with an orthographic, associative, or semantic relationship to a memory set item. The orthographic interference effects appeared to result from matches on the basis of abstract letter codes (i.e., graphemes) rather than overlap of visual features. The associative and semantic effects differed from what might be predicted on the basis of spreading activation, suggesting that these effects are qualitatively different from semantic priming effects observed in lexical decision tasks. These results support models of short-term memory in which items are represented as groups of features and recognition depends on a comparison of the features of the probe to those of the memory set items.

Humans↗
PubMed1997

Twelfth rib resection. Preferred therapy for subphrenic abscess in selected surgical patients.

OBJECTIVE: To assess the role of 12th rib resection in the treatment of postoperative, subphrenic abscesses. DESIGN: Consecutive case series. SETTING: University hospital, level I trauma center. PATIENTS: Operative logs for a 13-year period were reviewed for all patients undergoing 12th rib resection for drainage of a postoperative subphrenic abscess. Each individual medical record was reviewed for demographic data, primary diagnosis, computed tomographic scan findings, and clinical status (temperature, white blood cell count, and Acute, Physiologic, Age, and Chronic Health Evaluation II score) at the time of rib resection. MAIN OUTCOME MEASURES: Operative results, microbiological data, complications, and outcomes. RESULTS: Twenty-six patients underwent 27 rib resections for a secondary left subphrenic (23) or a right subhepatic (4) abscess. All patients had undergone at least 1 prior laparotomy (average, 1.5; range, 1-4). Sixteen patients had traumatic injuries, and 7 had complicated pancreatitis. Twelve patients had undergone prior failed attempts at percutaneous drainage before rib resection. Fourteen patients underwent operative drainage without attempted percutaneous drainage, mainly for peripancreatic (7) or multiloculated (3) abscesses. There were 3 postoperative complications (3/27 [11%]): a gastrocutaneous fistula, a gastrocolic-cutaneous fistula requiring laparotomy and temporary colostomy, and fasciitis in the resection site. Four (15%) of the 26 patients died: 3 died of progressive multiple system organ failure, and 1 died of an unrelated injury. The remaining 20 (77%) of the patients were discharged from the hospital with healing wounds and no further episodes of intra-abdominal infection. CONCLUSIONS: Twelfth rib resection is an effective alternative therapy for secondary subphrenic abscesses. The nature of the incision allows for open, dependent drainage; avoids subsequent laparotomy; and effectively controls intra-abdominal infections. Twelfth rib resection remains a useful tool in the treatment of subphrenic abscess and may be the preferred approach when other attempts at abscess drainage have failed.

Adult↗
PubMed1997

Protein processing and auxin response in transgenic tobacco harboring a putative cDNA of zeatin O-xylosyltransferase from Phaseolus vulgaris.

Zeatin is rapidly metabolized to O-xylosylzeatin in Phaseolus vulgaris seeds. The zeatin O-xylosyltransferase mediating this conversion, a 50 kDa protein, occurs mainly in the endosperm, both in the cytoplasm and the nuclei. A monoclonal antibody specific to the enzyme was used to isolate cDNAs from an expression library derived from P. vulgaris seeds. Two highly homologous, full-length cDNAs were isolated. The ORFs encode proteins of 69 and 67 kDa, respectively, with 90% homology at the amino acid level. cDNA-encoded protein obtained from in vitro transcription/translation was processed to protein of 50 kDa by bean endosperm extract. Transgenic tobacco plants harboring the larger ORF under the control of the CaMV35S promoter were more sensitive to the auxin NAA than control plants. The symptoms included leaf chlorosis, restriction of root elongation, and eventual cessation of growth. The antigenic preprotein was processed, and labeled zeatin was converted to O-xylosylzeatin in transgenic plants grown on NAA-containing medium. Analyses of independently transformed families indicated that the presence of the transgene coincided with the increased auxin sensitivity and protein processing correlated with the manifestation of auxin-induced damage. These results suggest that posttranslational processing regulates enzyme activity, and offer the possibility that cytokinin-auxin balance may be affected by stimulation of cytokinin metabolic enzyme activity by auxin.

Amino Acid Sequence↗
PubMed1996

Neuropsychological functioning in a patient with paraneoplastic limbic encephalitis.

A 54-year-old woman with clinically diagnosed paraneoplastic limbic encephalitis secondary to adenocarcinoma of the lung is described. Neuropsychological evaluation revealed intact visual perception, visual construction, language, speeded processing, and verbal abstract reasoning in the presence of a severe anterograde amnesia for both verbal and visual information. A profound consolidation problem is discussed in view of other diseases of the mesial temporal lobes resulting in impaired consolidation of new material.

Adenocarcinoma↗
PubMed1996

Differential vulnerability between postconcussion self-report and objective malingering tests in identifying simulated mild head injury.

The present study examined the ability of analog malingerers to feign postconcussion symptoms and neuropsychological performance patterns seen in mild head-injured patients. Experimental subjects were randomly assigned to either a control condition, asked to feign deficits consistent with mild head injury without task specific instruction, or feign deficits while given task-specific instruction. A separate group of mild head-injured patients served as a clinical comparison group. Analog malingering groups accurately simulated levels of postconcussive symptoms seen in the mild head-injured patients. However, poorer performance was displayed by the analog malingerers on the objective malingering tests. Coaching did not facilitate realistic patterns of performance for analog malingerers. The results of this study indicate that analog malingerers accurately replicated self-reported postconcussive symptoms, but were less able to simulate objective clinical malingering test performance. These results suggest that self-report measures of postconcussive symptoms and clinical tests are differentially vulnerable to simulation attempts.

Adolescent↗
PubMed1995

1H NMR studies of sarafotoxin SRTb, a nonselective endothelin receptor agonist, and IRL 1620, an ETB receptor-specific agonist.

1H NMR studies on the nonselective endothelin receptor agonist sarafotoxin SRTb have identified a helix between residues Asp 8 and His 16, and a beta-turn involving residues Cys 3 to Met 6; however, the biologically important C-terminal five residues were found to be conformationally variable. The average RMSD, measured for the final 43 refined structures to the average structure over residues 1-16, was 0.78 +/- 0.18 A for the backbone atoms and 1.39 +/- 0.22 A for all atoms. The torsion angles Cys 3 psi/Lys 4 theta, Thr 7 psi/Asp 8 theta and Gln 17 theta were identified as sites of conformational variability. Differences were found between the structures in the bicyclic loop region for SRTb and those published for ET1, another nonselective receptor agonist, which may explain the observed differences in potency of these peptides. The conformation of an ETB receptor-specific agonist, IRL 1620, which lacks the N-terminal seven residues and the two intrachain disulfides, was found by NMR and circular dichroism spectroscopy to be predominantly random coil, despite the fact that its affinity for the ETB receptor almost equals that of ET1. However, close analysis of the NMR results indicated the presence of turn-like structures, or a nascent helix, in the part of the sequence corresponding to the helical region in the parent peptides. These results suggest that the helical conformation may be required for ligand binding to the ETB receptor as well as to the ETA receptor.

Amino Acid Sequence↗
PubMed1995

Consequences of a motor programming deficit for rehearsal and written sentence comprehension.

The role of central motor processes in rehearsal was investigated by studying a brain-damaged patient with a severe articulatory impairment. Evidence is presented that his articulatory impairment is due to a disruption of motor programming rather than to peripheral muscle weakness. Despite his motor programming deficit, the patient showed normal auditory span and evidence of rehearsal for auditorily presented sequences of words. For visual presentation, span was reduced and there was no evidence of rehearsal. Also, the patient showed excellent sentence comprehension for syntactically complex sentences for both auditory and visual presentation. The results imply that central motor processes are not critical for normal short-term memory, at least for auditory presentation, and that reading comprehension does not depend on inner rehearsal.

Articulation Disorders↗
PubMed1994

Effects of phosphoramidon and pepstatin A on the secretion of endothelin-1 and big endothelin-1 by human umbilical vein endothelial cells: measurement by two-site enzyme-linked immunosorbent assays.

1. Two-site enzyme-linked immunosorbent assays have been developed for the rapid, sensitive and non-isotopic measurement of endothelin-1 and big endothelin-1. The sensitivities of detection were 0.5 and 0.3 fmol/well, with ED50 values of 13 and 12 fmol/well for the endothelin-1 and big endothelin-1 assays, respectively. Each assay is highly selective for its corresponding antigen. The ET-1 assay showed no detectable cross-reactivity with ET-1-(1-20), indicating that the assay only recognizes the 21-amino acid biologically active peptide. 2. The two assays were used to measure the effects of two classes of protease inhibitor on the basal release of enothelin-1 and big endothelin-1 from cultured first-passage human umbilical vein endothelial cells. 3. The secretion of both peptides was time-dependent over 12 h. The metalloprotease inhibitor phosphoramidon (1 x 10(-4) mol/l) significantly reduced the amount of endothelin-1 secreted into the medium (P < 0.05), with a concomitant increase in the secreted levels of big endothelin-1 (P < 0.01). The aspartyl protease inhibitor, pepstatin A, also caused a significant decrease in the secretion of endothelin (P < 0.05). However, unlike phosphoramidon, there was no increase in the levels of big ET-1 compared with the controls. At these concentrations, neither inhibitor affected the viability of the cells as indicated by Trypan Blue exclusion. 4. The two assays permit the direct measurement of endothelin-1 and its precursor, and will be of use in the elucidation of the putative human endothelin-converting enzyme(s).(ABSTRACT TRUNCATED AT 250 WORDS)

Antimalarials↗
PubMed1993

Cytolocalization of zeatin O-xylosyltransferase in Phaseolus.

Zeatin O-xylosyltransferase (EC 2.4.2.-) mediates the formation of O-xylosylzeatin from trans-zeatin and UDP-xylose in immature seeds of Phaseolus vulgaris. Tissue printing with a monoclonal antibody specific for the enzyme and a cDNA probe demonstrated that the enzyme was primarily localized and synthesized in the endosperm. Immunolocalization performed on monolayer endosperm at the free-nuclei stage and on EM sections demonstrated that the enzyme was associated with the nucleus as well as with the cytoplasm. Immunoanalysis of nuclear fractions revealed that the enzyme was retained in the nuclear pellet. Western analysis also showed that the enzyme was present in the nuclei of cotyledons and endosperm callus. The findings suggest that the enzyme may be involved in the nuclear-cytoplasmic transport of cytokinins and related molecules or, possibly, with chromatin of rapidly dividing cells.

Journal Article↗
PubMed1993

Effects of sophistication and motivation on the detection of malingered memory performance using a computerized forced-choice task.

The present study employed a computerized forced-choice recognition memory task, the Multi-Digit Memory Test (MDMT), to examine the effects of instructional set (i.e., dissimulation information provided subjects) and motivation (i.e., monetary incentive) on simulated malingering behavior in a group of 119 university undergraduate students and 33 patients sustaining varying severity of closed-head injury. For the nonpatient groups, a significant effect of instructional set was revealed. Motivational incentive, however, did not affect forced-choice performance. Overall, significant performance differences emerged between all groups with nonmalingering students performing nearly perfectly, the brain-injured patients performing well above chance levels, sophisticated student malingers performing at chance, and naive student malingers performing well below chance levels. These results suggest the MDMT may offer a clinically useful and convenient addition to a neuropsychological assessment when there is suspicion of feigned memory problems. These data also support the use of naive and sophisticated malingering subjects in further analog studies addressing this topic.

Adult↗
PubMed1993

Short-term memory and sentence processing: evidence from neuropsychology.

Traditional models of memory assume that short-term memory, as measured by memory span, plays an important role in linguistic processing and the learning of verbal information. Contradicting this view are findings from a brain-damaged patient, E.A., who, despite a verbal memory span of about two items, demonstrated normal sentence comprehension in a variety of tasks. She was, however, impaired whenever verbatim phonological information had to be maintained or learned. These results and those from other patients with reduced span suggest that the phonological storage capacity that is critical to memory span plays only a limited role in language processing, specifically in the maintenance and learning of phonological forms. Implications for models of short-term memory are discussed. It is argued that short-term memory should be seen as deriving from the processing and retentive capacities of language processing modules, with span tasks drawing on only a subset of these modules.

Attention↗
PubMed1992

Enzyme immunoassays for the estimation of adenosine 3',5' cyclic monophosphate and guanosine 3',5' cyclic monophosphate in biological fluids.

Simple, rapid and sensitive competitive enzyme immunoassays for the estimation of adenosine 3',5' cyclic monophosphate (cAMP) and guanosine 3',5' cyclic monophosphate (cGMP) in human plasma and urine are described. Specific antisera to each nucleotide were raised in rabbits by immunization with succinyl cyclic nucleotide--human serum albumin conjugates. For the assay, specific antibodies were incubated with a mixture of succinyl cyclic nucleotide labelled with horseradish peroxidase together with unlabelled standard or sample. The antibody-bound enzyme conjugate was separated from free hapten by anti-rabbit (IgG) sera immobilized to a microtitre plate. Activity of the bound enzyme conjugate was determined with tetramethylbenzidine. The assays were capable of detecting levels as low as 2 fmol of cAMP and cGMP. Good correlations were obtained between values generated by enzyme immunoassay and radioimmunoassay.

Animals↗
PubMed1992

How semantic is automatic semantic priming?

Priming for semantically related concepts was investigated using a lexical decision task designed to reveal automatic semantic priming. Two experiments provided further evidence that priming in a single presentation lexical decision task (McNamara & Altarriba, 1988) derives from automatic processes. Mediated priming, but no inhibition or backward priming was found in this type of lexical decision task. Experiments 3 and 4 demonstrated that automatic priming was found only for associated word pairs, as determined by word association norms, and not for word pairs that are semantically related but not associated. It is argued that automatic priming in the lexical decision task occurs at a lexical level not at a semantic level.

Adult↗
PubMed1991

Hippocampal contribution to verbal recent memory following dominant-hemisphere temporal lobectomy.

The effects of hippocampal encroachment in the language dominant-hemisphere were studied in 41 patients who underwent previous temporal lobectomy (TL). Patients undergoing dominant-hemisphere TL including anterior hippocampus (n = 13) performed significantly worse than nondominant TL patients (n = 16) on a verbal learning test (Selective Reminding; p less than or equal to .00001), thereby confirming the sensitivity of this procedure to lateralized temporal-lobe dysfunction. However, no significant difference was present on this or other primary measures of material-specific memory when contrasting dominant TL patients in whom the anterior hippocampus was spared (n = 12) to those in whom anterior hippocampus was resected. These data suggest that more extensive and posterior mesial temporal-lobe resection is not necessarily associated with a greater verbal material-specific memory deficit following dominant-hemisphere temporal lobectomy.

Adult↗