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Biomedical subjects

T Callahan

Publications and source records attributed to T Callahan.

10 recordsLinked to original sources
PubMed2000

Verbal working memory and solvent exposure: a positron emission tomography study.

Neuropsychological studies have documented frontal dysfunction in patients with a history of exposure to organic solvents. The deficits typically observed in these patients appear to be related to working memory (WM). This study used [15O] water positron emission tomography (PET) to examine the pattern of neural activation during verbal working memory in patients with a history of exposure to solvents. Six individuals with solvent exposure were compared with 6 age- and education-matched controls. On the 2 WM tasks examined with PET, with equivalent task performance, participants with solvent exposure demonstrated frontal peaks that were atypical for the tasks, whereas the posterior peaks were typical for the tasks. The results support frontal dysfunction and compensatory use within anterior regions of the WM system in patients with solvent exposure.

Brain↗
PubMed1996

Hemolytic reactions mechanically induced by kinked hemodialysis lines.

Ten hemolytic reactions occurred in our outpatient hemodialysis unit over a 12-month period (December 1989 to December 1990). Eight patients were hospitalized and one died. All patients developed severe abdominal or back pain an average of 2.5 hours into a 4-hour hemodialysis session using a bleach/formaldehyde reprocessed hollow-fiber cupraphan dialyzer (average reuse, three times) with blood flow rates of 375 mL/min. All had visible hemolysis in a spun hematocrit, seven had a significant decrease in hematocrit, and six developed pancreatitis. Hemolysis was further confirmed by a decrease in haptoglobin in all patients and an increase in lactic dehydrogenase in all but the last case. Investigation of each episode failed to find an abnormality in dialysate temperature or tonicity; dialysate or water levels of copper, zinc, nitrates, chloramine, or formaldehyde; or blood pump or venous alarm. Hemolytic reactions continued despite changing to 15-gauge needles, removing bleach from the reuse procedure, or stopping reuse. During the eighth episode, a kink was noted in the arterial blood line. Two subsequent hemolytic reactions occurred, and in each kinks were found in the arterial blood line, either in the excess tubing between the blood pump and drip chamber or in the predialyzer. No further hemolytic reactions occurred after changing to a new arterial blood line without redundant tubing and securing all lines. Hemolytic reactions occurring during hemodialysis have many etiologies, including mechanical trauma, which we report may result from kinking of dialyzer lines. With new blood lines on the market, attention to this aspect of dialysis is mandatory.

Abdominal Pain↗
PubMed1996

Factorial equivalence of the Wechsler Memory Scale: revised across standardization and clinical samples.

A two-phased analysis of the WMS-R is reported In the first phase, confirmatory factor analyses of the WMS-R standardization sample were conducted in order to identify a baseline model against which to compare two large samples of substance abusers These analyses revealed that most of the exploratory factor models reported in the literature were plausible representations of the WMS-R, however, a three-factor oblique model representing Attention/Concentration, Verbal Memory, and Visual Memory emerged as the best fitting model In the second phase, we conducted multi-sample factor analyses to test the generality of this model in two large samples of inpatients at an addiction recovery unit The results revealed that the factor loadings, subtest error variances (reliabilities), factor variances, and factor covariances were identical across groups Thus the factor structure of the WMS-R appears to be unaltered in these clinical groups Researchers may thus make meaningful comparisons of the dimensions indexed by the WMS-R between normal samples and neuropsychological groups with diffuse pathology.

Journal Article↗
PubMed1995

A case of bilateral thalamic lesions with anterograde amnesia and impaired implicit memory.

Thalamic nuclei appear to play an important role in memory functioning. Severe anterograde amnesia has been reported with lesions of the dorsomedial and anterior nuclei and their connections. We report the case of a woman with discrete thalamic lesions involving the anterior and dorsomedial nuclei who had a persistent anterograde amnesia. Contrary to a previous case report describing impairment only with explicit memory, this patient had impairment with both implicit and explicit memory. This case is discussed in terms of the relevant literature associating the diencephalon, amnesia, and implicit memory.

Clinical Conference↗
PubMed1993

Adolescent suicidal risk: psychological, problem solving, and environmental factors.

This study examined the life stress and problem-solving interactional model of suicide proposed by Clum, Patsiokas, and Luscomb (1979). Thirty-three hospitalized suicidal adolescents were compared with 21 adolescents hospitalized for other psychiatric problems and with 89 controls. The assessment battery was composed of psychological measures, problem-solving measures, and environmental and family measures. The discriminant analyses revealed that the suicide group could be discriminated from the psychiatric control group but not from the high school control group. Unexpectedly, life stresses did not contribute to the identification of current suicide risk. The results suggest the importance of assessing suicide risk at the time of admission to minimize any subsequent changes in the risk group.

Adaptation, Psychological↗
PubMed1987

Defining the active site of cytochrome P-450: the crystal and molecular structure of an inhibitor, SKF-525A.

The crystal and molecular structure of the cytochrome P-450 inhibitor, SKF-525A [2-(diethylamino)ethyl 2,2-diphenylpentenoate; proadifen hydrochloride] is described. Proadifen hydrochloride crystallized from an ethyl acetate and acetic acid mixture in the space group P2(1)/c with one molecule in the asymmetric unit. Cell constants are a = 18.716(4), b = 8.906(1), c = 14.201(3), beta = 109.41(1) degrees. The structure was solved using direct methods and was refined to an R value of 0.047; weighted R of 0.061 using 3757 reflections. From the crystal and molecular structure, it is seen that SKF-525A has two principal modes of complementary interactions with the enzyme available: polar and non-polar. Polar interactions that principally involve the chloride anion, the quaternary nitrogen atom and the carbonyl oxygen atom. In particular, there are two strong hydrogen bonds, one between Cl ... H-N, 3.090(1) A, the other between O2 ... H-C111 (one of the ethyl hydrogen atoms) at 3.411(2) A. The other is through non-polar interactions involving the phenyl and alkyl groups. Comparisons between proadifen hydrochloride and other inhibitors whose atomic coordinates are available reveal common features which correlate with their function. These include groups to provide necessary intermolecular contacts and bulk, such as a phenyl group and a hydrogen bond acceptor, as well as a tetrahedral atom, which allows for substrate flexibility.

Crystallization↗
PubMed1986

Characteristics of borderline personality disorder admissions to private psychiatric hospitals.

Inpatients diagnosed as having borderline personality disorder (BPD) by DSM-III criteria who were admitted to 11 Central Neuropsychiatric Hospital Association (CNPHA) hospitals in 1982 and 1983 are described in terms of 28 clinical-history and demographic characteristics. This study statistically compared 181 BPD inpatients to 1,121 non-BPD inpatients admitted to the same hospitals during the same period as part of the broader CNPHA prospective outcome study. These BPD inpatients were also compared to other BPD samples described in the literature. The 1982-83 CNPHA BPD inpatients exhibited clinical and demographic characteristics significantly different from their non-BPD counterparts. These BPD inpatients, mostly female, may have had particularly difficult living situations, had extensive treatment histories that began early, were frequently self-destructive, and had a distinctive medication pattern, among other characteristics. Comparison to other BPD samples in the literature showed similarities, supporting the generalizability of the CNPHA prospective outcome study.

Borderline Personality Disorder↗
PubMed1975

Thrombosis at the site of interruption of the vena cava: a consideration in prophylactic treatment of pulmonary embolism.

This study confirms the method of Ratnoff in inducing the hypercoagulable state in dogs, and further demonstrates that there is a varying thrombogenic factor when the vena cava is interrupted by ligation, staple plication, suture plication, serrated clip, and a smooth clip. The incidence of thrombosis caused by ligation, staple plication and suture plication would suggest that these are not suitable methods for prophylactic use. That no thrombosis occurred with the smooth clip would suggest that as a prophylactic measure, the smooth clip may be preferable to a serrated clip.

Animals↗