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Biomedical subjects

C A Morrison

Publications and source records attributed to C A Morrison.

At least 19 recordsLinked to original sources
PubMed2001

Spontaneous generation of stable pnictinyl radicals from "jack-in-the-box" dipnictines: a solid-state, gas-phase, and theoretical investigation of the origins of steric stabilization.

The molecular structures of the stable phosphinyl and arsinyl radicals, .PnR(2) [Pn = P (2); As (4); R = CH(SiMe(3))(2)], have been determined by gas-phase electron diffraction (GED) in conjunction with ab initio molecular orbital calculations. The X-ray crystal structures of the corresponding dipnictines, the "dimers", R(2)PnPnR(2) [Pn = P (1), As (3)], and the chloro derivatives R(2)PnCl [Pn = P (5), As (6)] have also been determined. Collectively, these structural investigations demonstrate that large distortions of the ligands attached to Pn occur when the pnictinyl radicals unite to form the corresponding dipnictine dimers. Principally, it is the shape and flexibility of the CH(SiMe(3))(2) ligands that permit the formation of the P-P and As-As bonds in 1and 3, respectively. However, theoretical studies indicate that in the process of pnictinyl radical dimerization to form 1 and 3, both molecules accumulate substantial amounts of potential energy and are thus primed to spring apart upon release from the solid state by melting, dissolution, or evaporation. The insights gleaned from these unusual systems have permitted a deeper understanding of the functioning of sterically demanding substituents.

Journal Article↗
PubMed2001

Preparation and properties of gallaborane, GaBH(6): structure of the gaseous molecule H(2)Ga(mu-H)(2)BH(2) as determined by vibrational, electron diffraction, and ab initio studies, and structure of the crystalline solid at 110 K as determined by X-ray diffraction.

Gallaborane (GaBH(6), 1), synthesized by the metathesis of LiBH(4) with [H(2)GaCl](n) at ca. 250 K, has been characterized by chemical analysis and by its IR and (1)H and (11)B NMR spectra. The IR spectrum of the vapor at low pressure implies the presence of only one species, viz. H(2)Ga(mu-H)(2)BH(2), with a diborane-like structure conforming to C(2v) symmetry. The structure of this molecule has been determined by gas-phase electron diffraction (GED) measurements afforced by the results of ab initio molecular orbital calculations. Hence the principal distances (r(alpha) in A) and angles ( angle(alpha) in deg) are as follows: r(Ga.B), 2.197(3); r(Ga-H(t)), 1.555(6); r(Ga-H(b)), 1.800(6); r(B-H(t)), 1.189(7); r(B-H(b)), 1.286(7); angleH(b)-Ga-H(b), 71.6(4); and angleH(b)-B-H(b), 110.0(5) (t = terminal, b = bridging). Aggregation of the molecules occurs in the condensed phases. X-ray crystallographic studies of a single crystal at 110 K reveal a polymeric network with helical chains made up of alternating pseudotetrahedral GaH(4) and BH(4) units linked through single hydrogen bridges; the average Ga.B distance is now 2.473(7) A. The compound decomposes in the condensed phases at temperatures exceeding ca. 240 K with the formation of elemental Ga and H(2) and B(2)H(6). The reactions with NH(3), Me(3)N, and Me(3)P are also described.

Journal Article↗
PubMed2001

Scanning laser polarimetry in a selected group of patients with glaucoma and normal controls.

PURPOSE: To evaluate the ability of scanning laser polarimetry to discriminate between subjects with glaucoma with specific patterns of visual field defect and normal controls. METHODS: This cross-sectional, prospective study in a glaucoma practice, focused on subjects with glaucoma with predefined types of visual field defect, including advanced (group A, n = 14), localized (group L, n = 46), or mixed (diffuse and localized) defects (group M, n = 22) and normal controls (n = 32). Scanning laser polarimetry was performed in one study eye per subject. Two methods of analysis were used: a subjective analysis, in which examination printouts with the image of the optic disk manually blocked were classified by two observers masked to the diagnosis, and a logistic regression analysis of the retardation parameters included in the printouts. RESULTS: The observers correctly identified 97% of the controls and 68% of subjects with glaucoma (overall correct classification of 77%), with 93%, 70%, and 47% of patients from groups A, L, and M, respectively, being correctly identified. The best discrimination obtained with the logistic regression correctly identified 69% of controls and 94% of glaucoma subjects (overall correct classification of 87%). The performance was only slightly better for cases from group A compared with L and M. CONCLUSIONS: Subjective assessment of the scanning laser polarimetry standard printout of single eyes might not be sensitive enough to detect cases of glaucoma with localized or milder mixed types of visual field defect. The discriminating ability of scanning laser polarimetry improves slightly when logistic regression analysis is employed.

Cross-Sectional Studies↗
PubMed2001

Using the exercise test to create the exercise prescription.

Exercise testing can provide valuable information to aid the primary care physician in developing a safe and effective exercise program for his or her patients. This review presents the most recent recommendations for the components of an exercise program as well as methods to accomplish appropriate prescription writing for the various subsets of individuals from the healthy patient to the patient with chronic disease. In addition, a plea is made for physicians to encourage all patients to engage in at least some kind of regular exercise activity in an attempt to counteract the increasingly sedentary lifestyles found in our culture.

Exercise Test↗
PubMed1998

Femoral venous flow dynamics during intraperitoneal and preperitoneal laparoscopic insufflation.

BACKGROUND: Laparoscopic herniorrhaphy may be performed using an intraperitoneal or a preperitoneal approach. Anecdotal and experimental evidence indicates that alterations in lower extremity venous flow, which occur during intraperitoneal laparoscopic insufflation, may be associated with an increased risk of deep vein thrombosis. However, no study has directly compared femoral venous flow during intraperitoneal insufflation with that during preperitoneal insufflation. METHOD: In eight consecutive patients undergoing laparoscopic herniorrhaphy under general anesthesia, flow through the common femoral vein was evaluated with B-mode and color flow duplex. Pre- and intraperitoneal pressures were standardized to 10 mm Hg, and respiratory tidal volumes were standardized to 10 cc/kg. Flow measurements were taken at end expiration. Flow through the common femoral vein was measured after induction of anesthesia, during intraperitoneal insufflation, during preperitoneal insufflation, and between insufflations to ensure return to baseline. RESULTS: All patients in the study were males. Their mean age was 59 years. Mean flow in the common femoral vein was essentially identical at baseline (138 ml/min) and during preperitoneal insufflation (135 ml/min). Alternatively, mean flow in the common femoral vein was significantly reduced during intraperitoneal insufflation (65 ml/min, p = 0.02). CONCLUSIONS: Flow in the common femoral vein is significantly reduced during intraperitoneal insufflation. However, flow in the common femoral vein is not affected by preperitoneal insufflation. These data suggest that laparoscopic preperitoneal inguinal hernia repair may pose as less a risk of thromboembolic complications than laparoscopic intraperitoneal inguinal hernia repair.

Adult↗
PubMed1998

Timing of vaccination does not affect antibody response or survival after pneumococcal challenge in splenectomized rats.

BACKGROUND: Pneumococcal vaccination after splenectomy for trauma decreases the incidence of overwhelming postsplenectomy infection. The optimal timing of vaccination has not been established. This study was conducted to determine whether timing of vaccination after splenectomy affects antibody response or survival after pneumococcal challenge. METHODS: Sprague-Dawley rats were used for all experiments. Control rats (n=30) were divided into three equal groups and underwent splenectomy followed by sham vaccination 1, 7, or 42 days after splenectomy. Treated rats (n=66) were divided into three equal groups and underwent splenectomy followed by vaccination with polyvalent pneumococcal vaccine 1, 7, or 42 days after splenectomy. All rats then underwent intraperitoneal Streptococcus pneumoniae inoculation with the predetermined lethal dose for 50% of the population 10 days after vaccination. Rats were observed for a 72-hour period after inoculation, and mortality was recorded. Immunoglobulin G and immunoglobulin M antibody titers were determined before vaccination and before inoculation to determine antibody response. RESULTS: Mortality was greater in the control group than in the treatment group (21 of 30 [70%] vs. 2 of 64 [3%]; p < 0.01). There were no differences in mortality within either the control group (1 day, 6 of 10; 7 days, 7 of 10; 42 days, 8 of 10; p=0.62) or the treatment group (1 day, 0 of 21; 7 days, 0 of 21; 42 days, 2 of 22; p=0.14). Immunoglobulin G and immunoglobulin M antibody responses were greater in vaccinated than in nonvaccinated rats. There was no effect of timing of vaccination on antibody response. CONCLUSION: Pneumococcal vaccine reduces mortality from postsplenectomy infection. Timing of vaccination after splenectomy does not affect survival from a pneumococcal challenge or antibody response in rats. This study supports the practice of administering vaccine within 24 hours of splenectomy when vaccine cannot be administered before surgery.

Animals↗
PubMed1997

Pharmacokinetics of the angiotensin-converting-enzyme inhibitor, benazepril, and its active metabolite, benazeprilat, in dog.

1. The pharmacokinetics of the angiotensin-converting-enzyme (ACE) inhibitor benazepril were evaluated in eight healthy Beagle dogs. Benazepril was administered orally at a dosage of 7.5 mg (about 0.5 mg/kg) both as a single dose and then once daily for 14 consecutive days. The prodrug, benazepril, and its active metabolite, benazeprilat, were measured in plasma using a gas chromatography mass-spectrometry method with mass-selective detection. 2. Benazepril appeared quickly in the plasma (tmax 0.5 h) and was rapidly eliminated by metabolism to benazeprilat. Peak benazeprilat concentrations were attained later (tmax 1.25 h) and declined biphasically with a rapid elimination phase (t1/2 lambda 1 1.1 and 1.7 h after single and the last repeated dose respectively) followed by a terminal elimination phase (t1/2 lambda z 11.7 and 19.0 h after single and repeated dose respectively). The mean residence time for benazeprilat was 15.2 h after the single dose and 17.4 h after the 14th dose. 3. Repeated administration of benazepril produced moderate bioaccumulation of benazeprilat; the ratio of AUC[0-->24 h]'s after the 14th dose as compared with the single dose was 1.47, equivalent to a half-life for accumulation (t1/2acc) of 14.6 h. Steady-state benazeprilat concentrations at peak (Cmax) and trough (Cmin) were reached within three doses. 4. The pharmacodynamics of benazepril were assessed by measurement of plasma ACE activity. After both single doses and at steady-state, benazepril produced inhibition of ACE activity in all dogs that was maximal at peak effect (Emax = 100%) and long-lasting (> 85% inhibition was present at 24 h). The long duration of action of benazepril on plasma ACE is due to the presence of the terminal elimination phase of benazeprilat, even though most of the metabolite is rapidly eliminated from the plasma.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1997

Brain attack: correlative anatomy.

Approximately 500,000 people suffer a new or recurrent brain attack each year. Despite advanced treatments, stroke continues to be the third leading cause of death in the United States. Survivors of stroke experience many different clinical problems and neurological deficits. Individual symptomatology varies according to specific vessel involvement and the location of brain tissue infarction or hemorrhage. Understanding basic cerebral anatomy provides a foundation for the neuroscience nurse to plan effective nursing care for the victim of brain attack.

Aged↗
PubMed1996

Protection of cattle against Fasciola hepatica infection by vaccination with glutathione S-transferase.

Glutathione S-transferase (GST) from the liver fluke Fasciola hepatica was assessed as a vaccine immunogen in cattle in a number of immunological adjuvants. Significant reductions in fluke burdens (49-69%) were only observed in cattle vaccinated with GST in Quil Alsqualene Montanide (SM) and PLG microspheres in SM but there was no correlation between anti-GST IgG titres and protection. In separate experiments, animals vaccinated with GST in Quil AlSM were still significantly protected (48%, P < 0.05) 6 months after boosting and no significant differences in protection were seen when the metacercarial challenge was given over 1 month instead of as a single bolus. Inhibition of GST enzyme activity in vitro by cattle antisera did not correlate with reduced fluke burdens.

Adjuvants, Immunologic↗