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Biomedical subjects

C Johnson

Publications and source records attributed to C Johnson.

At least 37 records · Page 2Linked to original sources
PubMed1994

Effects of increasing dietary polyunsaturated fatty acids within the guidelines of the AHA step 1 diet on plasma lipid and lipoprotein levels in normal males.

We attempted to ascertain the effects of polyunsaturated fatty acids by conducting two studies in normal young men, in which monounsaturated fats were replaced by polyunsaturated fats within the guidelines of the American Heart Association step 1 diet. Study A employed a randomized parallel design in which subjects first consumed an average American diet (AAD) containing 37% of calories as fat (saturated fat, 16% calories; monounsaturated fat, 14% calories; and polyunsaturated fat, 7% calories). After 3 weeks, one third of the subjects continued with the AAD, one third switched to a step 1 diet in which total fat calories were reduced to 30% by replacing saturated fat with carbohydrate, and one third switched to a polyunsaturated fat-enriched (Poly) diet with the same 30% fat calories and a reduction of monounsaturated fat from 14% to 8% and an increase of polyunsaturated fat from 7% to 13% of calories. The randomized period lasted 6 weeks. Total and low-density lipoprotein (LDL) cholesterol levels on the step 1 and Poly diets were reduced compared with levels on the AAD (P < .001). Total and LDL cholesterol did not differ between the step 1 and Poly diets, although comparison between the two diets is limited by the small study groups. Serum apolipoprotein (apo) B levels fell on the Poly diet compared with the AAD. Total high-density lipoprotein (HDL), HDL2, and HDL3 cholesterol levels were not significantly affected by the diets. Postprandial lipid and lipoprotein concentrations did not significantly differ either. In study B, a randomized crossover design was used in which all subjects ate the step 1 and Poly diets for 5 weeks each with a 4-day break between diets. In the eight subjects studied, the values for fasting plasma total, LDL, and HDL cholesterol; triglycerides; apoB; and apoA-I were essentially identical at the end of each diet period. Postprandial triglyceride areas obtained after ingestion of a large, standard fat load were also the same. Finally, LDL apoB and HDL apoA-I turnovers were unaffected by replacement of monounsaturates with polyunsaturates. In summary our results indicate that modest exchanges of monounsaturated for polyunsaturated fats do not significantly affect LDL or HDL levels or metabolism, which supports the view that reducing saturated fats is the key to lowering total and LDL cholesterol.

Adult↗
PubMed1994

Baseline silent cerebral infarction in the Asymptomatic Carotid Atherosclerosis Study.

BACKGROUND AND PURPOSE: In a group of patients with high-grade asymptomatic carotid artery stenosis, we prospectively determined the prevalence and radiological characteristics of clinically asymptomatic brain infarction evident on computed tomography. Risk factors and extent of carotid disease were also determined. METHODS: Patients randomized into the Asymptomatic Carotid Atherosclerosis Study (ACAS) underwent a neurological history, a detailed stroke/transient ischemic attack questionnaire, and a detailed neurological examination. Computed tomography scans were examined by standardized criteria developed as part of a quality-control program supervised by a neuroradiologist. The presence, location, and size of all cerebral infarctions evident by computed tomography were determined. RESULTS: Among 1132 patients, 848 had no history of stroke or transient ischemic attack. One hundred twenty-six patients (15%) had a silent infarct; 95 (11%) had one, 24 (3%) had two, and 7 (1%) had three or more infarcts. The infarct size was small and deep for 117 patients (72%), less than one-half lobe for 45 (28%), and one-half to less than one lobe for 1 (0.5%). The silent infarcts were evenly distributed ipsilaterally and contralaterally to the study artery but were significantly more frequent in the right hemisphere (P < .05). Factors associated with silent infarction were abnormal gait (P < .001), abnormal deep tendon reflexes or plantar responses (P = .038), but not degree of carotid stenosis. Silent infarction was less frequent among this totally asymptomatic cohort (15%) compared with those with transient ischemic attacks (34/139, 25%; P < .001). CONCLUSIONS: Silent infarction in the setting of asymptomatic carotid stenosis is not uncommon, but silent infarctions are rarely sizable. The clinical significance of silent cerebral infarction in patients with asymptomatic carotid artery stenosis has yet to be established.

Adult↗
PubMed1994

Do right-handers live longer? An updated assessment of baseball player data.

In support of the argument that left-handedness is a marker for decreased survival fitness, in 1991 Coren and Halpern gave considerable weight to the results of their 1988 study in which right-handed baseball players were described as having lived about eight months longer than their left-handed peers. In their 1993 unsuccessful attempt to replicate this study, Fudin and colleagues cited certain difficulties with the sources of these data that led them to recommend a comprehensive third study which included only reliable data from the two current editions of the major sources of information on Major League baseball players, i.e., the 1993 editions of The Baseball Encyclopedia and Total Baseball. Following this suggestion, we measured the life spans of all baseball players, i.e., right-, left-, and mixed-handed players, for whom reliable data were available (N = 5441) and found that the relationship between handedness and longevity was not significant. Unlike Halpern and Coren we noted that right-handed players could be described as having lived about eight months less than their left-handed peers.

Aged↗
PubMed1994

Beta-S gene cluster haplotypes modulate hematologic and hemorheologic expression in sickle cell anemia. Use in predicting clinical severity.

PURPOSE: The rate of progression of major organ failure in sickle cell anemia is genetically controlled. It is the direct consequence of the sickle cell-evoked vasculopathy. PATIENTS AND METHODS: Presence of the beta S gene cluster haplotypes and alpha gene deletions as genetic markers indicate the expected frequency of illness and the risk of end-stage major organ failure. The risk of irreversible soft tissue organ failure is greatest in patients with a Central African Republic (CAR) chromosome, whereas morbidity is consistently lowest in patients with a Senegalese chromosome. Presence of alpha-thalassemia-2 decreases the risk of soft tissue organ failure in all haplotype combinations. RESULTS: Other laboratory abnormalities, when combined with haplotype and alpha gene status, also predict the risk of clinical morbidity. The mean hemoglobin level (or red blood cell count) is lowest in patients with the most severe clinical manifestations. On the other hand, the platelet count and leukocyte count as well as the plasma fibrinogen level are elevated in the sickest patients. A threshold level of hemoglobin F at 1.2 g/dl (approximately 20% hemoglobin F) decreases the risk of major organ failure and is attained most frequently in those with a Senegalese chromosome. Hemorheologic findings observed during the most stable state of patients with sickle cell anemia indicate two trends: (a) the mean percentage of dense red cells is nearly twice as high in the maximal severity patients as compared with the minimal severity patients; and (b) mean red cell rigidity is greatest in the maximal severity group and least in the minimal severity group. These findings suggest that a greater percentage of dense, poorly deformable red cells are present in sickle cell patients in the genotypic category of maximal severity. CONCLUSIONS: The combination of the beta S gene cluster haplotype and alpha-gene status correlates with both phenotypic laboratory findings (hematologic profile) and morbidity. These associations increase our ability to predict clinical severity and the future risk of major organ failure.

Anemia, Sickle Cell↗
PubMed1994

Leukocytosis in labor: what are its implications?

OBJECTIVE: The objective of this study was to determine the usefulness of the peripheral white blood count (WBC) drawn during labor as a predictor of postpartum morbidity. METHOD: Hospital charts on 309 consecutive obstetrical deliveries performed by residents of the Cox Family Practice Residency were reviewed for evidence of maternal or neonatal postpartum morbidity. An analysis of means was used to compare the average antepartum WBC in the morbid and non-morbid groups. RESULTS: The average WBC in a laboring patient was 12,450, with a range of 4,400 to 29,100. Patients with postpartum complications had a WBC similar to that of patients without complications (12,900 vs 12,300 p = 0.449). CONCLUSION: An elevated WBC obtained on admission to the labor ward is not helpful in predicting postpartum complications in mothers or newborns.

Adolescent↗
PubMed1994

Tocolysis for recurrent preterm labor using a continuous subcutaneous infusion pump.

This study attempted to determine the best method of treatment for patients with recurrent preterm labor: administration of terbutaline via an automated, programmable, subcutaneous infusion pump or oral terbutaline. In this retrospective, controlled study, 32 patients diagnosed with recurrent preterm labor, as determined by persistent uterine contractions with cervical change, were treated with a programmable infusion pump adjusted to control uterine contraction frequency to < or = 4 contractions per hour. Patients in this group were matched for age, race, parity, gestational age and cervical dilation at diagnosis of recurrent preterm labor in subjects taking oral terbutaline. The patients receiving oral terbutaline were given an average of 6.5 mg every four to six hours to maintain uterine quiescence, while those in the pump group were given basal rates of terbutaline and in addition received four to six boluses per day (< 3 mg/d total dose) to achieve this outcome. Patients using the pump were more likely to reach term and less likely to fail tocolytic therapy than were those taking oral terbutaline. The terbutaline pump appeared to be more successful in prolonging pregnancies to term after the diagnosis of recurrent preterm labor than did oral terbutaline.

Administration, Oral↗
PubMed1994

Further mapping of the properdin deficiency gene in a Tunisian Jewish family--evidence for genetic homogeneity.

The properdin deficiency gene has been localized to Xp21.1-Xcen; however, it is not clear whether the mutation responsible for the disease co-maps exactly with the structural properdin gene. Based on a recent study on a total of six families, the gene was found linked to DXS255 (theta = 0.00). As only a few families have been studied, it is not known whether the same gene is responsible for the disease in all families. In order to better localize the disease gene in Israel, we studied a Tunisian Jewish family with properdin deficiency for linkage with various X-markers. A maximum lod score of 1.93 at theta = 0.00 was calculated with the DXS7 probe while there was one recombination with DXS255. This study helps to better localize the properdin deficiency gene to Xp11.3-p21.1 proximal to DXS255 locus and confirms that there is no indication of genetic heterogeneity. Whether the properdin structural gene (PFC) and properdin deficiency locus are one and the same await demonstration of mutations in the structural gene in patients with properdin deficiency.

Chromosome Mapping↗
PubMed1994

The airway in the obstetrical patient.

Airway management of the parturient has serious implications for the anesthetist. Meticulous patient evaluation and preparation is essential. A management plan that can be implemented in the event of failed intubation should be familiar to all anesthetists who are involved in obstetrical anesthesia.

Anesthesia, Obstetrical↗
PubMed1994

Evaluation of autologous shed blood for autotransfusion after orthopaedic surgery.

Autologous shed blood for autotransfusion was evaluated at four medical centers in a prospective randomized study. One hundred twenty-eight patients were studied after hip replacement, knee replacement, or spine fusion. The efficacy of autologous shed blood in reducing homologous transfusion was evaluated. The relative risk of transfusion with homologous blood was 0.4 in patients who received shed blood compared with patients who did not receive shed blood. The reinfusion of shed blood reduced the requirement for homologous blood by 60%. Two filter systems were evaluated in reinfusing autologous shed blood. The Pall RC100 filter appeared to be more effective than the Pall 40-mu screen filter in removing fat particles and white blood cells. No significant clinical abnormalities were discovered after autotransfusion with autologous shed blood. Evaluation of clotting studies showed no significant differences between patients who received shed blood and patients who received liquid-preserved red blood cells. These data indicate that unwashed autologous shed blood from orthopaedic wound drainage is a safe and effective substitute for transfusion of autologous predonated blood or homologous liquid-preserved red blood cells.

Adult↗
PubMed1994

OKT 3 reaction in a renal transplant patient.

In this case, the intended patient outcomes were achieved. Nursing was clearly able to take a very proactive role in providing the necessary emergency patient care to prevent further patient compromise. Once the immediate physiologic danger of respiratory decompensation was treated, nursing moved on to intervene in the less-serious complications associated with OKT 3 reaction to assure maximal patient comfort. Finally, patient teaching was done both to assess the learning needs associated with the OKT 3 reaction, as well as to prepare the patient and family for administration of additional doses of OKT 3. These nursing actions resulted in a very favorable outcome for both the patient and family.

Humans↗
PubMed1993

Agonist pharmacology of the neuronal alpha 7 nicotinic receptor expressed in Xenopus oocytes.

The potencies and efficacies of seven agonists at chick alpha 7 nicotinic receptors expressed in Xenopus oocytes were determined by whole cell recording. (+)-Anatoxin-a was the most potent agonist (EC50 = 0.58 microM) and acetylcholine was the least potent (EC50 = 320 microM). The rank order of agonist potencies was: (+)-anatoxin-a >> cytisine > (-)-nicotine > (+)-nicotine > DMPP > 1-acetyl-4-methylpiperazine methiodide > acetylcholine. DMPP evoked only very small currents: comparison of maximally effective agonist concentrations showed that DMPP was only one-fifth as efficacious as other agonists. Previously published IC50 values for rat brain [125I]alpha-bungarotoxin sites show a similar agonist profile, and the identity of homo-oligomeric alpha 7 receptors with native alpha-bungarotoxin-sensitive neuronal nicotinic receptors is discussed.

Acetylcholine↗
PubMed1993

Germ line transmission of a yeast artificial chromosome spanning the murine alpha 1(I) collagen locus.

Molecular complementation of mutant phenotypes by transgenic technology is a potentially important tool for gene identification. A technology was developed that allows the transfer of a physically intact yeast artificial chromosome (YAC) into the germ line of the mouse. A purified 150-kilobase YAC encompassing the murine gene Col1a1 was efficiently introduced into embryonic stem (ES) cells via lipofection. Chimeric founder mice were derived from two transfected ES cell clones. These chimeras transmitted the full length transgene through the germ line, generating two transgenic mouse strains. Transgene expression was visualized as nascent transcripts in interphase nuclei and quantitated by ribonuclease protection analysis. Both assays indicated that the transgene was expressed at levels comparable to the endogenous collagen gene.

Animals↗
PubMed1993

Biochemical control, genetic analysis and magnetic resonance imaging in patients with phenylketonuria.

Thirteen patients with phenylketonuria, detected by neonatal screening and started on diet within 16 days of age, were investigated between 10 and 18 years of age by magnetic resonance imaging (MRI) of the brain. Biochemical control was assessed from: (1) the life time blood phenylalanine (Phe) control (as determined from (a) the mean yearly exposure to Phe; (b) the accumulated time for each patient that Phe was < 120 mumol/l; (c) > 400 mumol/l; (d) > 800 mumol/l; and (e) > 1200 mumol/l); and (2) the blood Phe control over the 5 years prior to imaging (assessed for each patient by the mean yearly Phe exposure over that period). In all patients the phenylalanine hydroxylase gene locus was studied using restriction fragment length polymorphism haplotypes and mutant genes were screened for a variety of specific mutations which have been reported in other European populations or in populations of north European descent. Two patients had significant abnormalities of cerebral white matter. Although both showed poor biochemical control this did not reach statistical significance when compared to those with normal imaging. DNA haplotype patterns could be assigned to 11 patients and mutant genes were identified in 12. One patient with abnormal imaging and 4 patients without abnormalities had mutations on both chromosomes identified. In these 5 patients there was significant correlation between their genotype and biochemical control. Mutations resulting in residual in vitro enzyme activity were associated with normal imaging.

Adolescent↗
PubMed1993

Multisystem damage associated with tricorporal priapism in sickle cell disease.

PURPOSE: Priapism is an uncommon but debilitating complication of sickle cell disease (SCD). Recent observations among adult males regarding the abysmal failure of medical and surgical therapy encouraged us to review our 25-year experience identifying the prognostic features that might determine outcome. PATIENTS AND METHODS: As part of a prospective 25-year longitudinal demographic and clinical cohort study, a subset of 38 (8.2%) patients with priapism were identified among a cohort of 461 men with SCD. The patients with priapism were compared with the nonaffected men with respect to severity of disease expression, hematologic status, beta s globin gene haplotype, and the incidence of sickle-related major organ failure. The influence of the treatment modalities on outcome was also evaluated. RESULTS: Priapism occurred as a single episode in 24 patients, and in 14 as temporally clustered repeat episodes. Eighty-seven percent of those with priapism had sickle cell anemia (SS), an increased risk as compared with other variants of SCD (p = < 0.05). There were two distinct age-related patterns of disease expression. Eight patients were prepubertal; they experienced shorter episodes, involvement of the corpora cavernosa only, few recurrent episodes, and a good prognosis for future erectile function. Non-surgical therapy in children was associated with excellent results. In contrast, the 29 postpubertal adults often had involvement of the corpora cavernosa and corpus spongiosa (tricorporal disease) and half had prolonged episodes that lasted longer than 8 days. One pubescent patient had repeated episodes and became impotent. Prolonged or repeated episodes eventuated in impotence in 56%. Surgical intervention was not beneficial. Sickle cell-related organ failure such as stroke, chronic restrictive lung disease, chronic renal failure, and nonhealing leg ulcers was observed more frequently in men who had priapism. Death occurred in nine adult patients (25%) within 5 years of the first episode of priapism. CONCLUSION: Priapism in adult males identifies those at high risk for other sickle cell-related organ failure syndromes and, as such, is another complication indicative of severe disease. The dismal prognosis in SS adults requires better understanding of the precise pathophysiology of low-flow tricorporal priapism. Clarification of the mechanisms inducing the priapic state should lead to specific therapeutic maneuvers and an improved prognosis for this disabling condition.

Adolescent↗
PubMed1993

Iron-deficiency anemia: a medically treatable chronic anemia as a model for transfusion overuse.

PURPOSE: Transfusion practice in patients with iron deficiency was reviewed. PATIENTS AND METHODS: During the study period, records of 265 consecutive patients with an unsaturated iron-binding capacity of greater than 53.7 mumol/L were evaluated for possible iron-deficiency anemia. RESULTS: Two hundred sixty-three patients met the study criteria for iron deficiency. Of these patients, 50 received 1 or more units of red blood cells (RBCs). The transfusion therapy of 12 patients could not be justified; physicians used laboratory results rather than the clinical status of the patients to initiate transfusion therapy. As a result, units of RBCs were transfused to raise the hematocrit to an arbitrarily chosen level. Furthermore, iron therapy was not prescribed for 97 of the 263 iron-deficient patients, including 11 of the patients for whom transfusion was justifiable and 2 patients for whom transfusion could not be justified. Based on records reviewed, no work-up was initiated to identify the cause of iron deficiency in 13 patients, including 4 patients who received transfusions. CONCLUSION: These findings suggest that the evaluation and treatment of iron deficiency, including transfusion therapy for that condition, may be problematic. In view of the risks of blood transfusion therapy, improvement in transfusion practices for iron deficiency should be emphasized.

Anemia, Hypochromic↗
PubMed1993

Evaporation versus iced peritoneal lavage treatment of heatstroke: comparative efficacy in a canine model.

The authors compared the speed of cooling and treatment efficacy for evaporative cooling versus iced peritoneal lavage in a canine heatstroke model. Nine random-source, mongrel dogs were anesthetized, shaved, and internally heated until the core temperature reached 43.0 degrees C. The animals were then randomly assigned to be cooled to 37 degrees C either by sterile normal saline (6 degrees C) continuous peritoneal lavage at 250 mL/min (n = 4), or by spraying with tap water (15 degrees C, 12 L/min) before a large fan blowing room temperature air (23 degrees C) across the dog at 0.5 m/sec from a height of 50 cm (n = 5). Temperatures were monitored by thermocouples in both tympanic membranes. Electrocardiogram, blood pressure, and pulse were continuously monitored. Evaporative cooling was as rapid as iced peritoneal lavage (0.18 +/- .03 versus 0.17 +/- .07 degrees C/min/m2, P = NS). All animals survived, although one animal in each treatment group demonstrated a moderate neurologic deficit when measured 48 hours following resuscitation. A simple noninvasive evaporative cooling technique, readily available in the emergency department, appears to be as rapid readily available in the emergency department, appears to be as rapid and effective as aggressive peritoneal lavage for cooling and treating heatstroke in the dog.

Animals↗