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Biomedical subjects

K Allen

Publications and source records attributed to K Allen.

At least 127 records · Page 7Linked to original sources
PubMed1985

The effect of paraquat on the mutagenicity of benzo(a)pyrene.

Elevated activities of superoxide dismutase (SOD) were detected in histidine-requiring strains of Salmonella typhimurium after the bacteria were preincubated for 1 h at 37 degrees C with S-9 mix and paraquat (methylviologen, PQ2+) at 10(-4) M. A fivefold increase in SOD level was found for strains TA 98 and TA 100. These elevated levels of SOD activity were correlated with a significant reduction of the mutagenicity of metabolically activated benzo(a)pyrene (B(a)P) in these tester bacteria when evaluated in a preincubation assay system. A 69.0-92.5% and 23.5-66.9% reduction was noticed when 0.5-4.0 micrograms per plate of B(a)P was used in TA 98 and TA 100, respectively. However, exogenous superoxide dismutase at 10-100 micrograms ml-1 added to top agar had no significant effect on the number of revertants produced by activated B(a)P. These data indicate a major role of intracellular superoxide anion in promoting mutagenicity of B(a)P.

Animals↗
PubMed1984

Genetic analysis of adenine metabolism in Leishmania donovani promastigotes. Evidence for diploidy at the adenine phosphoribosyltransferase locus.

Mutant promastigotes of Leishmania donovani deficient in adenine phosphoribosyltransferase (AP-Rib transferase) have been isolated in medium containing 4-aminopyrazolopyrimidine. The generation of AP-Rib transferase-deficient mutants occurred in two discrete steps. In the first step, clones were isolated with 50% of wild-type levels of AP-Rib transferase activity. These cells were reselected, and colonies totally deficient in AP-Rib transferase were isolated. Wild-type and AP-Rib transferase-deficient cells contained equivalent amounts of other enzymes essential to adenine metabolism such as adenine deaminase and hypoxanthine-guanine phosphoribosyltransferase. Partially and totally AP-Rib transferase-deficient cells exhibited intermediate and complete resistance to cytotoxic adenine analogs, respectively. Nevertheless, wild-type and mutant cells could salvage adenine and utilize adenine as a purine source equally efficiently, suggesting that the adenine deaminase-hypoxanthine-guanine phosphoribosyl-transferase pathway plays an important role in promastigote adenine metabolism. Kinetic and thermal inactivation studies of purified AP-Rib transferase and isoelectric focusing of crude extracts from wild-type and partially AP-Rib transferase-deficient cells suggested that the latter cells possessed wild-type AP-Rib transferase activity at half the amount found in wild-type parental cells. These data suggest that L. donovani possesses two copies of the AP-Rib transferase structural gene and that these organisms might be diploid for the AP-Rib transferase locus.

Adenine↗
PubMedDate not supplied

Brain metabolism and blood flow in acute cerebral hypoxia studied by NMR spectroscopy and hydrogen clearance.

We have developed a reliable, reproducible model of hypoxia in the gerbil. 1H and 31P NMR spectroscopy demonstrates that cerebral energy metabolism is very resistant to hypoxia. Cerebral blood flow (measured by hydrogen clearance) began to increase when the arterial oxygen tension (paO2) was reduced to 40-50 mm Hg, and there was no change in phosphorus metabolites or lactate until paO2 was below 40 mm Hg. In 50% of the animals lactate increased prior to any change in the phosphorus metabolites or intracellular pH, suggesting that 1H NMR may be more sensitive than 31P NMR at detecting hypoxic or ischaemic changes. The calculated rate of oxygen delivery at a time when phosphorus energy metabolism becomes impaired is similar in both hypoxia and ischaemia (ca 4mL/100 g/min). We suggest that the critical factor in ischaemia is the reduction in oxygen supply, rather than the accumulation of toxic metabolites, such as lactate.

Animals↗
PubMedDate not supplied

Normalization of hypertensive responses during ambulatory surgical stress by perioperative music.

OBJECTIVE: The purpose of this study was to determine whether cognitive appraisals of stress level and hypertensive responses to ambulatory ophthalmic surgery can be ameliorated by patient-selected music. METHODS: We studied 40 elderly individuals requiring ophthalmic surgery, 20 in an experimental group (mean age, 74 years) and 20 in a control group (mean age, 77 years). All patients had an established resting blood pressure <140/90 mm Hg. In the experimental group self-selected music was provided by headphones throughout the preoperative, surgical, and postoperative periods. In the control group patients had neither headphones nor music. All patients received similar (weight-determined) doses of alfentanil and midazolam during surgery. Heart rate, blood pressure, and patient-reported stress and coping levels were the dependent variables. RESULTS: In both groups, blood pressure values were normal (approximately 129/82 mm Hg) during screening examinations 1 week before surgery. On the day of surgery both groups displayed increased preoperative blood pressures (approximately 159/92 mm Hg) associated with increases in heart rate (by approximately 17 beats/min). Intraoperative blood pressures in the experimental group returned quickly to screening baseline values, whereas the control group experienced persistent elevations in intraoperative blood pressure similar to preoperative levels. Over the course of the surgical experience, patients with music reported significant reductions in perceived stress and increases in coping abilities (p < .001), whereas those without music did not. CONCLUSIONS: The perceived stress of ambulatory surgery in geriatric patients is associated with a clinical hypertensive response that is ameliorated by self-selected perioperative music, which also decreases perceived stress and increases patients' sense of personal control and well-being.

Acoustic Stimulation↗
PubMedDate not supplied

Use of hydroxyurea in children ages 2 to 5 years with sickle cell disease.

The efficacy and side effects of hydroxyurea in young children with sickle cell disease are unknown. The authors followed-up eight young children (mean age 3.7 years) during therapy with hydroxyurea for an average of 137 weeks. Total and fetal hemoglobin levels rose with hydroxyurea therapy. Hospital admission rates and total hospital days decreased during hydroxyurea therapy. No unexpected toxicity occurred, and growth and development were unaffected. This pilot study suggests that hydroxyurea is safe and effective in young children with sickle cell disease.

Anemia, Sickle Cell↗
PubMedDate not supplied

Posterior ventricular septal rupture: an anatomical reconstruction.

Rupture of the ventricular septum following posterior myocardial infarction is an uncommon, but lethal, injury that requires prompt repair. Surgical reconstruction can be complex, demanding, and unfamiliar. Conventional techniques, as described in the literature, are associated with a variety of potential pitfalls. An alternative method we have successfully used in our last four patients is presented in detail. The procedure uses two composite (felt/pericardium) patches: an internal patch to reconstruct the left ventricular geometry and an external patch to repair the subtotal infarctectomy. For maximal security, all suture lines sandwich myocardium between two continuous felt surfaces. Specific transition stitches are described, which reliably anchor the entire repair at the critical, but poorly visualized, areas where the ventricular septum makes its transition to left and right ventricular free walls. This technique offers immediate hemostasis and a more anatomical left ventricular geometry. The method also reduces the risk of systemic thromboembolism, residual VSD, and repair disruption.

Aged↗
PubMedDate not supplied

Bonding amalgam to tooth structure: a scanning electron microscope study.

The purpose of this scanning electron microscope study was to observe the interface between dentin and amalgam utilizing various adhesive resin cements. The adhesive resin materials used in this study were Imperva Dual, Geristore, and Panavia. The scanning electron micrographs revealed that bonds were established between amalgam, adhesive resins, and dentin.

Dental Amalgam↗
PubMedDate not supplied

Effect of exercise on urinary N-acetyl-beta-D-glucosaminidase activity and albumin excretion in children with type I diabetes mellitus.

Urinary N-acetyl-beta-D-glucosaminidase (NAG), a proximal tubule lysosomal enzyme, has been used as an indicator of subtle renal injury. Since it has been positively and significantly correlated with hemoglobin A1c and microalbuminuria, it has been suggested that this enzyme may also reflect metabolic control. Albumin excretion is exacerbated in adult diabetic individuals during exercise; such exercise-induced albuminuria may be a forerunner of diabetic nephropathy. Metabolic control, degree of exertion, and duration of diabetes have been suggested to influence this increase in albuminuria during exercise. Studies of children are few and have produced inconsistent results. Thus we studied 28 insulin-dependent diabetic children ranging in age from 5 yr to 16 yr and 27 age-matched controls using treadmill exercise; two exercise periods consisting of (1) graded increases in speed and grade at 3-min intervals until exhaustion and (2) a constant speed and grade necessary to produce 2/3-3/4 maximal heart rate for 30 min were performed. Capillary blood glucose, urinary NAG/creatinine (cr) ratios (UNAG/Ucr) and urinary albumin/creatinine ratio (Ualb/Ucr) were measured before and after each exercise period; hemoglobin A1c was also measured. The latter averaged 11.8 +/- 0.6% (mean +/- SEM); contrary to previous studies, this was not correlated with pre- or postexercise UNAG/Ucr. During both exercise periods, blood glucose dropped 271 +/- 19 mg/dl to 213 +/- 21 mg/dl (period 1) and 230 +/- 22 mg/dl to 157 +/- 21 mg/dl (period 2).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylglucosaminidase↗
PubMedDate not supplied

Current morale issues that impede the caregiving process of substance abuse/addictions nurses.

A telephone survey was conducted with 25 nurse managers of substance abuse/addictions programs in a metropolitan area to ascertain what morale issues impede the caregiving processes of their nursing staff. Five issues were repeatedly identified by all 25 nurse managers. Those issues were: (a) lack of credibility and respect for the nurse in the eyes of other members of the multidisciplinary team, (b) lack of understanding of the role of nurses in the substance abuse/addictions program on an inpatient unit; (c) lack of adequate preparation for the role, (d) lack of acceptance of the nursing role as defined by nursing, and (e) the care of patients with concurrent diagnoses. This article analyzes these issues from the perspective of reasons for existence and possible solutions.

Attitude of Health Personnel↗
PubMedDate not supplied

Affective symptoms in the chronic stage of traumatic brain injury: a study of married couples.

A convenient sample of 60 brain-injured subjects and their spouses was evaluated cross-sectionally in the chronic stage of recovery on self-rated measures of sensory, motor, cognitive and behavioural disability and on the SCL-90-R depression and anxiety subscales. A majority of the brain-injured subjects, who were on average almost 6 years post-injury, demonstrated elevations on the affective symptom scales, with almost 70% showing depression and 50% showing anxiety. The spouses of the brain-injured individuals also demonstrated significantly elevated affective symptom scales, with 73% acknowledging symptoms of depression and 55% demonstrating symptoms of anxiety. For the individuals with brain injury, those with higher self-ratings of cognitive disability and social aggression had higher self-ratings of depression and anxiety. In contrast, spouse gender appeared to have the greatest association with the presence of elevation affective responses, with female spouses having higher levels of depression and anxiety than male spouses. These findings are discussed in terms of the reactionary nature of affective disturbances in the chronic stage of recovery.

Activities of Daily Living↗
PubMedDate not supplied

Efficacy of a computerized local anesthesia device in pediatric dentistry.

PURPOSE: The purpose of this study was to evaluate the efficacy of a computerized anesthesia delivery system in reducing pain during injections when compared with a traditional delivery system (i.e., syringe). METHODS: Subjects consisted of 57 patients between the ages of 5 and 13 needing operative dentistry using local anesthesia. Patients were randomly assigned to either the computerized or traditional anesthesia delivery system. Inferior alveolar block injections, palatal, and buccal infiltrations were the only injections administered throughout this study. Pain behavior was videotaped and coded throughout the study. Pain perceptions were rated using a 10 point visual analogue rating scale. Subjects were also asked to rate their overall satisfaction and approval of the dentist and the treatment received. RESULTS: Results of multivariate analysis of variance indicated that there were no significant differences between the computerized and the traditional method of administering local anesthesia when comparing pain ratings and pain behavior. Average pain ratings for the computerized method were 4.5 while the average ratings for the traditional method were 3.6. In addition, all subjects reported overall satisfaction with their dental treatment and that they would be willing to return in the future. CONCLUSIONS: A computerized anesthesia injection method was found to be comparable to the traditional method of anesthesia injection.

Adolescent↗