Biomedical subjects

C R Clark

Publications and source records attributed to C R Clark.

245 records · Page 14Linked to original sources

PubMedDate not supplied

Multicomponent spectroscopic assay for hemoglobin and ferrihemoglobin species in methemoglobin treatment of cyanide poisoning.

Monitoring the concentrations of various hemoglobin and ferrihemoglobin species and their cyanide complexes is important in the study of the efficacy of methemoglobin-forming agents for the treatment of cyanide toxicity. In this study, the visible absorption spectra of three hemoglobin intermediates were experimentally determined and compared with computer-generated spectra. The data supported the assumption that the molar absorptivities of the intermediates are equivalent to the combined absorptivities of the component subunits. A multicomponent Fourier transform (FT)-aided full spectrum quantitation system (FSQ) to simultaneously measure hemoglobin (Hb), hemimethemoglobin (hemiMetHb), and the cyanide complex dicyanohemimethemoglobin (dicyhemiMetHb) was also evaluated. It was found that FSQ had satisfactory accuracy and precision to quantitate hemiMetHb and dicyhemiMetHb at concentrations from 2 to 20% of the total Hb, a range commonly encountered in the treatment of cyanide poisoning using methemoglobin-forming agents. The simplicity and rapid throughput of the method make it suitable for clinical evaluation studies and form the basis for the design of a portable instrument for field analysis of these species.

Calibration↗

PubMedDate not supplied

Comparative anticonvulsant activity and neurotoxicity of 4-amino-N-(2,6-dimethylphenyl)benzamide and prototype antiepileptic drugs in mice and rats.

The anticonvulsant and toxic properties of 4-amino-N-(2,6-dimethylphenyl)benzamide, (ADD 75073), were compared with phenytoin (PHT), phenobarbital (PB), ethosuximide (ESM), and valproate (VPA). These compounds were evaluated in mice and rats using well-standardized anticonvulsant test procedures. The results indicate that ADD 75073 is a very potent anticonvulsant in the maximal electroshock seizure (MES) model. The compound was effective in nontoxic doses following intraperitoneal (i.p.) administration in mice and oral administration in both mice and rats. In mice, the i.p. administration of ADD 75073 resulted in an ED50 value of 2.6 mg/kg as compared with a value of 9.5 mg/kg for phenytoin (PHT) in the same assay. Compound ADD 75073 was ineffective in nontoxic doses against all other seizure models examined in this study, and thus has a pharmacologic profile similar to that of PHT.

Animals↗

PubMedDate not supplied

Pharmacological effects of enantiomers of 4-amino-N-(alpha-methylbenzyl)benzamide, a chemically novel anticonvulsant.

LY 188544,S,R-4-amino-N-(alpha-methylbenzyl) benzamide, and its two stereoisomers are structurally novel anticonvulsants. The anticonvulsant profile of LY 188544 after intraperitoneal administration to mice was determined in standard anticonvulsant tests: maximal electric shock (MES), strychnine tonic-extensor, and threshold tests using pentylenetetrazol, picrotoxin, and bicuculline. In this series of tests, LY 188544 had good activity in the MES test and some activity in the three threshold tests. Thus, its profile of activity was most similar to that of phenobarbital, and less similar to that of phenytoin and carbamazepine. After oral administration to mice and rats, LY188544 was effective in the MES test, but did not provide complete protection in the threshold pentylenetetrazol test. When the individual stereoisomers, LY188545 (S isomer) and LY188546 (R isomer), were evaluated after oral administration, LY188545 was 2.2 times more potent than LY188546 against MES-induced seizures. However, when evaluated after intravenous administration, the potency difference was only 1.1. LY188546 was the least toxic in terms of neurological impairment. All compounds had good protective indexes (ratio between doses for neurological impairment and doses for anticonvulsant efficacy in the MES test). LY188545 and LY188546 potentiated hexobarbital sleeping time after acute administration but not after chronic (4-day) administration. Tolerance did not develop to the effects of LY188546 on MES or neurological impairment after 4 days of administration. These results suggest that LY188546 is a chemically novel anticonvulsant with a promising pharmacological profile.

Animals↗

PubMedDate not supplied

Comparative anticonvulsant activity of 4-chlorobenzenesulfonamide and prototype antiepileptic drugs in rodents.

The anticonvulsant and toxic properties of 4-chlorobenzenesulfonamide (ADD 55051) were compared with phenytoin (PHT), phenobarbital (PB), ethosuximide (ESM), and valproate (VPA). These compounds were evaluated in mice and rats using well-standardized anti-convulsant test procedures. The results indicate that ADD 55051 is a very effective anticonvulsant in the maximal electroshock seizure (MES) model in mice after either intraperitoneal (i.p.) or oral administration and in rats after oral administration. In mice treated i.p. or orally, ADD 55051 was also effective in preventing seizures induced by pentylenetetrazol (PTZ). The toxicity of ADD 55051 after oral administration was quite low, yielding high TD50 values in both mice and rats and producing a very high protective index (PI = TD50/ED50) in both species as compared with the prototype antiepileptic drugs (AEDs).

Animals↗

PubMedDate not supplied

Colposcopy: sensory information for client education.

OBJECTIVE: To determine women's sensory experiences during colposcopy and to describe a model for developing sensory information. DESIGN: Four-stage survey design, which included standardizing the procedure, discovering the experience, validating the experience, and writing the message. SETTING: Ambulatory clinics in a large teaching hospital in New Brunswick, Canada. PARTICIPANTS: Sixty women undergoing colposcopy. RESULTS: A valid sensory information message for colposcopy was documented. A model for developing sensory information was derived from a critical appraisal of the four-stage process. The merits of validation interviews were reinforced. CONCLUSIONS: The step-by-step approach outlined in the developmental model provides nurses with precise guidelines for developing other sensory messages. Nurses using a prepared message, such as that provided for colposcopy, need to ensure that it is accurate for their practice setting.

Adolescent↗

PubMedDate not supplied

Event-related potential measurement of deficits in information processing following moderate to severe closed head injury.

Event-related potentials may offer more precision than behavioural measures for understanding the extent and timing of information processing difficulties that follow closed head injury (CHI). Behavioural tests consistently indicate a general reduction in cognitive function but lack adequate diagnostic or prognostic function. This study compares a group of seven CHI patients, in which time since injury varied between 1 and 5 years following injury, with 10 matched controls on a three-tone discrimination task. Abnormality in the processing of tones as early as 200 ms following their onset, as measured by the P2 and N2 components of the event-related potential, indicated a general difficulty with tone discrimination. This abnormality was obtained despite differing damage profiles over patients and is likely to be due to the diffuse aspects of damage normal in CHI. These results also indicate that functional deficits in CHI patients can extend up to 5 years or more. A correlation between P2/N2 amplitudes and time since injury, however, suggests that both these components normalize with the passage of time and offers the prospect of a sensitive, non-behavioural measure of recovery in cognitive processing.

Adolescent↗

PubMedDate not supplied

St Loye's Independent Living Centre: an analysis of assessments.

An analysis of 1156 assessment forms was carried out in order to: (a) provide a baseline for an evaluation study, and (b) enable service characteristics to be developed. It was estimated that 1156 accounted for 70% of the total number of disabled people who visited the centre over a 5-year period. The assessments, completed by an experienced occupational therapist (OT), recorded demographic details and some of the problems encountered by disabled people with daily living activities. The greatest demand for the service came from the over-60 age group and, in particular, women aged between 70 and 79 years. A total of 79% (n = 693) of referrals were made by health workers; of that number, 81% (n = 561) were referred by an OT. Few referrals came from general practitioners. The most frequently reported medical condition affected the musculoskeletal system. The most frequently reported problem with daily living activities was bathing/showering. The amount of time spent on an assessment occupied a large proportion of the OT's capacity. Implications for the service are discussed.

Activities of Daily Living↗

PubMedDate not supplied

Synthesis, identification, and acute toxicity of some N-alkyl derivatives of 3,4-methylenedioxyamphetamine.

A series of N-alkyl derivatives of 3,4-methylenedioxyamphetamine (MDA) was prepared in an effort to characterize these potential drugs of abuse. These secondary amines were synthesized via reductive amination of the corresponding ketone with alkylamines. The ultraviolet absorption spectra for these compounds produced almost equally intense absorbance at 234 and 285 nm. The compounds were separated by liquid chromatography using reverse phase (C18) procedures with a ternary mobile phase mixture. Toxicity studies showed all of the compounds to have LD50 values similar to N-methyl MDA (MDMA).

3,4-Methylenedioxyamphetamine↗

PubMedDate not supplied

Synthesis, identification, and acute toxicity of alpha-benzylphenethylamine and alpha-benzyl-N-methylphenethylamine. Contaminants in clandestine preparation of amphetamine and methamphetamine.

Amphetamine samples obtained from clandestine laboratories often contain other by-product amines. The most common of these are the alpha-benzylphenethylamine derivatives. This article reports the independent synthesis of reference samples of these amines, spectrophotometric and chromatographic methods for their identification, as well as acute toxicological studies. The utility of the analytical methods is demonstrated by the analysis of several amphetamine samples containing these alpha-benzylphenethylamines.

Amphetamine↗

PubMedDate not supplied

Immune deficiency, thrombocytopenia and osteomyelitis in pediatric patients.

Surgical decompression of osteomyelitis in pediatric patients should be an essential part of therapy in most cases. The initial deferral of prompt decompression in two patients because of underlying chronic, hemorrhagic (thrombocytopenic) disorders-one with Wiskott-Aldrich syndrome and one with Gaucher's disease-resulted in more serious and prolonged courses of the infectious processes. The complications might have been ameliorated by earlier drainage in each case. Based upon the experience gained from these two patients, we recommend early drainage, with appropriate treatment of the hemorrhagic disorder, to prevent more widespread dissemination or prolongation of osseous infection in similarly affected children.

Adolescent↗

PubMedDate not supplied

Cervical spine arthrodesis in rheumatoid arthritis: a long-term follow-up.

Forty-one patients with rheumatoid arthritis involving the cervical spine had a posterior cervical arthrodesis. They were followed for a minimum period of seven years. The diagnoses prior to surgery included cranial settling, atlantoaxial subluxation, subaxial subluxation, and any combination of these three. All patients had posterior arthrodesis, with or without methylmethacrylate, and iliac crest autogenous bone graft. In addition, one patient had an anterior vertebrectomy, and two had transoral resection of the odontoid. Follow-up consisted of a subjective questionnaire, standard radiographs, and physical examination, including a neurologic exam. This information was compared to preoperative data available in the patient's medical record, postoperative data, and the information obtained in a similar study undertaken in 1987. At the time of follow-up, thirteen patients were known to be dead. One patient could not be located. Of the remaining twenty-six patients, eighteen underwent the full examination, including physical exam and radiographs. The remaining nine patients were contacted and interviewed, but were unavailable for exam and radiographs. All patients considered the operation a success. Only one patient at follow-up had a non-union. This was stable over time. No patient had a deterioration in neurologic function. There was no significant degeneration or instability seen at levels adjacent to the fused segments as compared to the rest of the cervical spine. Posterior cervical spine arthrodesis for rheumatoid involvement of the neck is a safe, efficacious procedure with no significant deterioration of effects over time.

Arthritis, Rheumatoid↗