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Biomedical subjects

W Marks

Publications and source records attributed to W Marks.

At least 19 recordsLinked to original sources
PubMed2005

New onset geriatric epilepsy: a randomized study of gabapentin, lamotrigine, and carbamazepine.

OBJECTIVE: To determine the relative tolerability and efficacy of two newer antiepileptic drugs, lamotrigine (LTG) and gabapentin (GBP), as compared to carbamazepine (CBZ) in older patients with epilepsy. METHODS: This was an 18-center, randomized, double-blind, double dummy, parallel study of 593 elderly subjects with newly diagnosed seizures. Patients were randomly assigned to one of three treatment groups: GBP 1,500 mg/day, LTG 150 mg/day, CBZ 600 mg/day. The primary outcome measure was retention in trial for 12 months. RESULTS: Mean age was 72 years. The most common etiology was cerebral infarction. Patients had multiple medical conditions and took an average of seven comedications. Mean plasma levels at 6 weeks were as follows: GBP 8.67 +/- 4.83 microg/mL, LTG 2.87 +/- 1.60 microg/mL, CBZ 6.79 +/- 2.92 microg/mL. They remained stable throughout the trial. Early terminations: LTG 44.2%, GBP 51%, CBZ 64.5% (p = 0.0002). Significant paired comparisons: LTG vs CBZ: p < 0.0001; GBP vs CBZ: p = 0.008. Terminations for adverse events: LTG 12.1%, GBP 21.6%, CBZ 31% (p = 0.001). Significant paired comparisons: LTG vs CBZ: p < 0.0001; LTG vs GBP: p = 0.015. There were no significant differences in seizure free rate at 12 months. CONCLUSIONS: The main limiting factor in patient retention was adverse drug reactions. Patients taking lamotrigine (LTG) or gabapentin (GBP) did better than those taking carbamazepine. Seizure control was similar among groups. LTG and GBP should be considered as initial therapy for older patients with newly diagnosed seizures.

Aged↗
PubMed2005

Livers transplanted from donors after cardiac death occurring in the ICU or the operating room have excellent outcomes.

BACKGROUND: Increasing donor hospital cooperation with donation after cardiac death (DCD) requires the organ procurement organization (OPO) to use current withdrawal of life support (WLS) protocols. Hospital ICU nurses/physicians are comfortable performing the emotionally draining procedure of WLS in the ICU while OPOs are reluctant to accept these donors due to increased warm ischemia (WI). In our area, several hospitals will only allow WLS to occur in the ICU. This study compares liver outcomes from DCD donors where death occurred in the ICU (DCDICU) vs the OR (DCDOR). METHODS: From March 2003 to June 2004, 34 DCD donors were recovered by our OPO. WLS occurred in the ICU for 26 donors (76%) and in the OR for 8 donors (24%). Thirteen of 26 DCDICU and 5 of 8 DCDOR livers were transplanted. Donor demographics, warm ischemic time, cold ischemic time, distance shipped, and recipient functions were analyzed. RESULTS: Eighteen livers were transplanted both locally and at distant transplant centers. Results are outlined in the . CONCLUSIONS: Although DCDICU donors averaged approximately 4 minutes longer WI than DCDOR donors, short-term results for both groups were equivalent. These findings support using DCDICU livers. DCDICU donors have the potential to significantly improve donor hospital cooperation.

Adult↗
PubMed2001

Impaired recruitment of bone-marrow-derived endothelial and hematopoietic precursor cells blocks tumor angiogenesis and growth.

The role of bone marrow (BM)-derived precursor cells in tumor angiogenesis is not known. We demonstrate here that tumor angiogenesis is associated with recruitment of hematopoietic and circulating endothelial precursor cells (CEPs). We used the angiogenic defective, tumor resistant Id-mutant mice to show that transplantation of wild-type BM or vascular endothelial growth factor (VEGF)-mobilized stem cells restore tumor angiogenesis and growth. We detected donor-derived CEPs throughout the neovessels of tumors and Matrigel-plugs in an Id1+/-Id3-/- host, which were associated with VEGF-receptor-1-positive (VEGFR1+) myeloid cells. The angiogenic defect in Id-mutant mice was due to impaired VEGF-driven mobilization of VEGFR2+ CEPs and impaired proliferation and incorporation of VEGFR1+ cells. Although targeting of either VEGFR1 or VEGFR2 alone partially blocks the growth of tumors, inhibition of both VEGFR1 and VEGFR2 was necessary to completely ablate tumor growth. These data demonstrate that recruitment of VEGF-responsive BM-derived precursors is necessary and sufficient for tumor angiogenesis and suggest new clinical strategies to block tumor growth.

Animals↗
PubMed2001

Encoding processes and attentional inhibition in directed forgetting.

Lexical decisions were used to evaluate whether forget (F)-cued prime words affect subsequent encoding of target words relative to remember (R)-cued prime words. In 3 experiments, R-cued primes were better recalled than F-cued primes. Targets that followed F-cued primes were responded to faster than targets that followed R-cued primes in same-case and different-case identity priming. Semantic priming occurred for targets that followed both types of memory-cued primes. However, response times were longer for both related and unrelated targets following R-cued primes relative to F-cued primes. These results indicate that R and F items are processed to similar levels of representation and inhibitory mechanisms do not attenuate encoding of F items. However, there is slower access to working memory for information that follows R-cued items.

Adult↗
PubMed1999

Effect of maternal diabetes on the fetal exocrine pancreas.

To test the hypothesis that fetal pancreatic exocrine and endocrine function are stimulated in parallel in the diabetic pregnancy, 68 mothers with gestational and pregestational diabetes who underwent amniocenteses after 34 weeks' for the evaluation of fetal lung maturity were enrolled. Amniotic fluid specimens were analyzed for C-peptide and trypsin content. Amniotic fluid specimens were obtained from 92 non-diabetic women undergoing amniocenteses for lung maturity, preterm labor, or premature rupture of membranes. Groups were compared using the Wilcoxon rank-sum test, Kruskal Wallis rank sum test, and Spearman's rank correlation test. C-peptide amniotic fluid concentrations were significantly greater in diabetics (median 0.6 ng/ml) than non-diabetics (median 0.4 ng/ml, P= 0.0001), in pregestational (median 0.6 ng/ml) vs. gestational diabetics (median 0.4 ng/ml, P = 0.006), and greater in proportion to severity of disease according to diabetic class (A1 = 0.4 ng/ml, A2 = 0.55 ng/ml, B = 0.6 ng/ml, C = 0.7 ng/ml, D = 0.85 ng/ml, P = 0.04). No significant differences were detected in amniotic fluid trypsin between the diabetic and non-diabetic or the gestational and non-gestational diabetic groups. There was no correlation between C-peptide and trypsin within the diabetic groups. Stimulation of the exocrine and endocrine pancreas does not occur in parallel in the fetus of the diabetic mother. Although originating as a single organ, pancreatic exocrine and endocrine functions are distinct in both physiologic and pathologic conditions.

Adult↗
PubMed1999

Age-related deficits in generation and manipulation of mental images: I. The role of sensorimotor speed and working memory.

The authors investigated age-related slowing of information processing in mental imagery tasks. Eighty-five healthy adults (ages 18 to 77) performed a visual, sensorimotor, reaction-time task; a visual-perceptual choice reaction task; and 3 mental imagery tasks that varied in apparent difficulty and involved stimuli at 2 levels of graphic complexity. Age was associated with prolongation of response time across all tasks and both levels of stimulus complexity. Accuracy of response was adversely affected by increase in stimulus complexity in all tasks, whereas it was negatively related to age only on the tasks with substantial mental imagery requirements. Slowing of information processing and reduction in accuracy were mediated by declines in working memory but not by decrease of sensorimotor speed.

Adult↗
PubMed1995

Amino acid sequence analysis, gene construction, cloning, and expression of gelonin, a toxin derived from Gelonium multiflorum.

The plant toxin gelonin is an extremely potent inhibitor of protein synthesis, similar in action to ricin. The mature protein primary sequence was obtained using conventional sequencing techniques. Gelonin was found to be composed of 258 amino acids and contains 21 lysine residues. This toxin shares approximately 33% sequence homology with trichosanthin and ricin A chain. A 774 bp synthetic gene encoding gelonin was synthesized and expressed in E. coli. Recombinant gelonin (approximately 28 kD) expression was monitored and demonstrated by western analysis. Purification and functional activity studies demonstrated that this protein behaves identically to that of the natural product. Recombinant gelonin (RG) thus joins a growing list of recombinant toxins currently available for use in the construction of recombinant immunotoxins composed of gelonin fused to binding domains of antibodies, growth factors, or other cytokines.

Amino Acid Sequence↗
PubMed1992

Effects of severe closed-head injury on three stages of information processing.

The present study investigated the loci of the information-processing delay that characteristically follows severe closed-head injury (CHI). Sternberg's additive-factors logic was used to determine the effects of severe CHI on the central information-processing stages of stimulus encoding, memory comparison, and decision-making/response-selection. The task variables used to define the stages operationally were stimulus quality, memory set size, and stimulus-response compatibility. Twenty subjects who had sustained a severe CHI more than 18 months earlier and 20 matched control subjects completed a stimulus encoding by response selection task in Experiment 1, and a Sternberg high-speed memory scanning task in Experiment 2. The CHI group performed the stimulus encoding and decision-making/response-selection stages of processing significantly slower than did the control group. However, no significant group differences were found on the memory comparison stage, suggesting that memory comparison processes may be relatively intact in long-term patients with severe head trauma. The results are discussed in relation to a global and a late-specificity hypothesis of central processing deficits following severe CHI. The possibility that cognitive processes demanding less attention may be more resilient to injury is also considered.

Adult↗
PubMed1992

Physical restraints in the practice of medicine. Current concepts.

OBJECTIVE: This article reviews the current status of the utilization of physical restraints in the practice of medicine. Based on current data from the reference sources, appropriate guidelines for the utilization of physical restraints in the practice of medicine are presented. DATA SOURCES: A review of the current literature as referenced in the article. Only English-language references were used. STUDY DESIGN: Articles were selected based on a review of articles from Index Medicus, English-language only. Articles were reviewed by the author for validity and appropriateness. DATA EXTRACTION: The guidelines of data quality, validity, and appropriateness were applied to all articles by the author. DATA SYNTHESIS: Restraints are frequently used in the practice of medicine. As many as 85% of nursing home patients will be restrained at some time and up to 17% of hospitalized medical patients will be restrained. This treatment is not always appropriate but there are no current guidelines available for the practicing physician to assist him or her in these decisions. The current use of physical restraints is discussed. The risks of restraints are reviewed and the reasons for restraint use are cited. The question regarding the efficacy of restraints is directly addressed for each of the situations in which restraints are most commonly used. The ethical and legal considerations concerning the use of restraints are reviewed, current concepts are summarized, and guidelines for improved usage of restraints are suggested. CONCLUSIONS: Despite their extensive use, there is virtually no evidence to support the efficacy of restraints. The risks of using mechanical restraints are numerous and well documented. The detrimental psychologic impact of restraints needs to be emphasized. Restraints are inappropriately used if employed because of fear of liability should a patient fall. The proper approach to the patient at risk of falling is to address the contributing factors that place the patient at risk and, where possible, correct them. Restraints are overused in medicine. Guidelines are given to help improve the employment of this potentially harmful practice.

Accidental Falls↗
PubMed1991

Effects of encoding the perceptual features of pictures on memory.

Four experiments investigated whether manipulations of type of encoding affects the likelihood of remembering pictures' visual details and their names. Using an incidental learning procedures, subjects were led to make judgments about pictures' colors, spatial orientations, or appropriateness in a scene. The results indicate that the nature of the memory test influences the effectiveness of different encoding conditions. Recall and recognition of pictures' names were best after subjects judged scene encodings, second best after they judged orientation, and poorest after they judged color. However, the results for the recognition of pictures' visual details were quite different. Analyses of d' suggested that type of encoding task had no effect on memory for visual details, whereas analysis of Pr (hit rate minus false-alarm rate) suggested that memory for visual details was impaired by conceptual encoding (judging the appropriateness of a picture in a scene). The results of one experiment demonstrated that these findings were not produced by variation in distinctiveness of the encoding questions. This pattern of findings implies that conceptual encoding facilitates retention of the names of the pictures at the cost of some loss in the ability to retain specific visual details.

Adult↗
PubMed1991

[Cavernosography using digital luminescence radiography (DLR) in the diagnosis of venous induced erectile function and of diseases of the corpus cavernosum].

Dynamic cavernosography is the most important technique for identifying and localizing venous leakage in erectile dysfunction. The use of digital radiography with a greater degree of tolerance in the exposure, a more dynamic signal, and a shorter exposure time can enhance the diagnostic value of conventional cavernosography. A further advantage of the method is the lower dosage required, which means that the gonads are exposed to less radiation. For 30 patients with erectile dysfunction and 7 other cases, conventional cavernosography images were compared with those obtained by this new method. The advantages of digital radiography are discussed.

Adult↗
PubMed1990

Quantitative morphometric analysis of brain growth using magnetic resonance imaging.

Using a simple image analysis system, we have established normative data obtained from magnetic resonance imaging (MRI) scans for the relative size and growth of the major structural domains of the brain. Midsagittal scans of the head were analyzed in 95 subjects aged 0 to 20 years. Only scans with no demonstrable structural abnormalities of the brain were utilized. Age-related changes in the relative growth of specific structures were calculated by dividing patients into 5-year age increments. No age-related changes were found in the size of the posterior fossa, supratentorial intracranial space, or cisterna magna relative to the total intracranial vault space. A significant (P less than .01) increase in the size of the corpus callosum relative to that of the supratentorial structures and relative to the total intracranial vault space was noted to occur between the 6- to 10-year-old and 11- to 15-year-old age groups. This may reflect an increase in myelination of the corpus callosum that occurs during this period. A small reduction in the ratio of the posterior fossa to the supratentorial space was found between the 0- to 5-year-old and the 6- to 10-year-old age groups, but the biological significance of this difference is uncertain. It appears from these data that quantitative analysis of MRI scans can be used to draw objective conclusions about the relative sizes and growth of the major brain structures. The development of normative data for these structures and the simplicity of the methodology should have many clinical applications in the assessment of aberrant brain development.

Adolescent↗
PubMed1990

[Comparative contrast media studies using conventional film-screen systems and digital luminescence radiography].

This is a report on the clinical application of digital luminescence radiographs compared to conventional x-rays during examinations with contrast medium. We present selected examinations of the period October to December 1988. By a constant quality of hard copies the digital examinations are equal to conventional x-rays. Regions of little difference in density are better represented by digital luminescence radiographs.

Contrast Media↗
PubMed1989

Elaborative processing of pictures in verbal domains.

Four experiments were performed to evaluate the effect of semantic and nonsemantic verbal elaboration of the names of pictures on free recall, picture-name recognition, and picture recognition. Elaboration was manipulated by having subjects decide if the names of pictures contained two letters, rhymed with another word, or were appropriate in a sentence frame. Semantic elaboration of the names of pictures in sentence contexts requiring positive responses resulted in better name recall (Experiment 1) and name recognition (Experiments 1 and 2) than did nonsemantic elaborations (rhyme- and letter-identification tasks). However, the effects of elaborating pictures' names were greatly reduced for picture recognition (Experiments 3 and 4). The results are described in terms of elaborative processing after semantic access. Following initial semantic access, the names of pictures may be further elaborated. Semantic elaboration of the names of pictures typically leads to better retention than does nonsemantic elaboration. However, perceptual records about the appearance of objects may be relatively independent of orienting tasks that elaborate pictures' names.

Attention↗
PubMed1987

Retrieval constraints on associative elaborations.

This research investigated the role of associative elaborations on free- and cued-recall performance. Elaboration was manipulated by having subjects pronounce an associatively related word that could be integrated into an activated episodic trace following sentence-encoding operations on the target concept. In Experiments 1 and 2, free recall was facilitated when the word was related to the sentence context of the target encoding compared to when it was related only to the target, or both the target and the context. The target-related conditions did not differ from an unrelated control condition for positive response encodings. This same pattern held for cued recall when the sentence frame context was provided as the retrieval cue (Experiment 1). However, Experiment 2 showed that if the elaborating word was provided as a cue for the target, then recall was highest when it was related to both the target and its context or only to the target. The results are discussed in terms of retrieval constraints on associative elaborations.

Association↗