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Biomedical subjects

H C Brown

Publications and source records attributed to H C Brown.

36 records · Page 2Linked to original sources
PubMed1988

The relapse of Trypanosoma brucei brucei infections after chemotherapy in rabbits.

Infections of T. brucei in the rabbit were found to relapse after chemotherapy. The results indicated that 25 mg/kg diminazene aceturate given 3 days after infection resulted in a complete cure but if given 7 days after infection relapses frequently occurred. However, treatment was apparently successful if delayed until 14 or 21 days. Six of the rabbits originally treated with diminazene aceturate on day 7 were treated with suramin 21 days later; in 3 rabbits the infections relapsed. In all rabbits in which drug treatment was not curative, the clinical condition nevertheless improved. An attempt to locate a cryptic focus of infection in rabbits was unsuccessful.

Amidines↗
PubMed1984

Early enteral feeding of patients with major burns: prevention of catabolism.

The immediate onset of hypermetabolism after a major burn dictates that nitrogen and calories be supplied as early as possible to such patients to prevent the well-documented catabolic state. However, intravenous hyperalimentation is not always possible, and enteral feeding is not usually attempted in the early resuscitative period. Twelve patients with major burns (40% to 70%) were fed nasoduodenally in the early postburn period with a new solution (3.5% Aminosyn, 25% Polycose, and appropriate additions of electrolytes and vitamins). All patients reached positive nitrogen balance in 9.8 +/- 2.3 days, tolerated the feeding extremely well, and had no distention or diarrhea. Metabolic assessment showed remarkable stability. The characteristic signs of hypermetabolism, such as hyperglycemia and hypoinsulinemia or hyperinsulinemia, were absent. Furthermore, there was no persistent neutrophilia or leukocytosis and there was a significant (p less than .01) decrease in the percentage of juvenile neutrophils and a significant (p less than 0.001) increase in absolute lymphocytes between days 0 and 14 of the study. These data indicate that early enteral feeding of Polycose-Aminosyn is safe and well tolerated, and that the small intestine absorbs nutrients readily in the early postburn period, leading to positive nitrogen balance, preventing loss of serum protein, assisting in the maintenance of normal carbohydrate metabolism, and restoring granulocytes and lymphocytes to normal ratios.

Blood Cell Count↗
PubMed1980

Structural effects in solvolytic reactions; carbon-13 NMR studies of carbocations: Effect of increasing electron demand on the carbon-13 NMR shifts in substituted tert-cumyl and 1-aryl-1-cyclopentyl carbocations-correlation of the data by a new set of substituent constants, sigma.

The cationic carbon substituent chemical shifts (DeltadeltaC(+)) for nine representative meta-substituted tert-cumyl carbocations are correlated satisfactorily by the sigma(m) (+) substituent constants (slope rho+ = -18.18, correlation coefficient r = 0.990). However, the substituent chemical shifts (DeltadeltaC(+)) for the corresponding para derivatives are not correlated by the sigma(p) (+) substituent constants. The possibility of developing a set of substituent constants capable of correlating such (13)C NMR shifts was examined. The slope of the line defined by the meta substituents (rho+ = -18.18) was utilized to calculate sigma(C+) constants for both meta and para substituents. The utility of these constants was then tested by their ability to correlate the (13)C NMR shifts in the cations for a different system, the 1-aryl-1-cyclopentyl cations. Indeed, these sigma(C+) values correlate very well with the DeltadeltaC(+) values, yielding rho(C+) = -16.84, r = 0.999.

Journal Article↗
PubMed1980

Hydroboration kinetics: Unusual kinetics for the reaction of 9-borabicyclo[3.3.1]nonane with representative alkenes.

The kinetics of hydroboration of alkenes with 9-borabicyclo[3.3.1]nonane dimer, (9-BBN)(2), exhibit interesting characteristics. With more reactive alkenes, such as 1-hexene, 2-methyl-1-pentene, 3,3-dimethyl-1-butene, and cyclopentene, the reaction exhibits first-order kinetics, first order in (9-BBN)(2) and zero order in alkene. On the other hand, with less reactive alkenes, such as cyclohexene, 1-methylcyclohexene, and 2,3-dimethyl-2-butene, the reaction exhibits three-halves-order kinetics, first order in alkene and one-half order in (9-BBN)(2). These kinetics can be accounted for in terms of the following mechanism:(9-BBN)(2) right arrow over left arrow 2 9-BBN9-BBN + alkene --> B-alkyl-9-BBNIn the case of the more reactive alkenes, the rate-determining step is the dissociation of the dimer. With less reactive alkenes, the reaction of the alkene with the monomer becomes the rate-determining step. For certain alkenes, such as 2-methyl-2-butene and cis-3-hexene, neither of the two steps is a decisive rate-determining step. Therefore, the reaction exhibits kinetic behavior between that of first- and three-halves-order kinetics.

Journal Article↗
PubMed1978

Management of extremity with combined neurovascular and musculoskeletal trauma.

Twenty-five civilians with combined neurovascular and musculo-skeletal trauma to 27 extremities were studied retrospectively. The mechanism of injury was crushing in 16, avulstion in six, and penetrating in three. Autogenous saphenous vein was used to restore arterial circulation in the majority. Nine patients had concurrent repair of venous injuries. Fractures were immobilized by a variety of techniques, the Hoffman external skeletal fixation being preferred. Immediate fasciotomy was performed in five patients and delayed fasciotomy in four. All patients had soft-tissue debridement and initial wound closure with split-skin grafts as biologic dressings. Three immediate amputations were the result of irreversible neurovascular and soft-tissue trauma. Sepsis played a role in three late amputations; delayed primary treatment,, irreversible neurologic injuries and extensive soft-tissue damage contributed. A carefully individualized multidisciplinary approach resulted in salvage of 20 of 27 severely injured extremities.

Adolescent↗
PubMed1977

Common injuries of the athlete's hand.

Hand injuries are among the most frequent accidents seen in sports medicine. All too commonly they are considered trivial since the athlete may continue to participate actively and neglect his injury. The consequent delay in diagnosis and proper treatment may result in long-standing or even permanent disability. This paper describes the more commonly encountered hand injuries, their diagnosis and their optimal treatment. Included are soft-tissue injuries, ligamentous injuries, fractures and tendon avulsions. The basic principles applicable to skeletal and soft-tissue trauma of the hand, which physicians at all levels of sports medicine may encounter, are stressed.

Athletic Injuries↗
PubMed1977

Influence of intrinsic sympathomimetic activity and cardioselectivity on beta adrenoceptor blockade.

Dose-response curves for propranolol and oxprenolol were studied in healthy volunteers, with a standardized excercise test and percentage reduction in excercise heart rate (EHR) as the index of drug effect. The dose-response curves obtained were compared with similar curves previously reported for sotalol, practolol, and atenolol with identical experimental methods. Two distinct types of response were identified: in the first, shown by propranolol and sotalol, increasing doses of the beta adrenoceptor-blocking drug continued to produce increasing effects to the limits of the dose levels examined; with the second (oxprenolol and practolol), increasing the dose initially resulted in substantial increase in effect but subsequently larger doses produced almost no increase in effect. Consideration of the additional properties of these beta adrenoceptor-blocking drugs revealed that both practolol and oxprenolol have intrinsic sympathomimetric activity (ISA), whereas propranolol and sotalol do not. In addition, practolol is cardioselective. Further investigation of the possible influence of ISA or cardioselectivity on beta adrenoceptor-blocking activity was undertaken by studying the effects of combinations of drugs on EHR. Sotalol produced greater effect when given 2 hr after sotalol, oxprenolol, practolol, or atenolol. When oxprenolol was given after sotalol or oxprenolol, or practolol was given after sotalol or practolol, there was no further increase in percentage reduction in EHR. When atenolol was given, the combinations of sotalol and atenolol together with two doses either of sotalol or atenolol all induced increases and similar final percentage reductions in EHR. Thus atenolol induces effects like those of sotalol, which are quite different from those of oxprenolol or practolol. The presence or absence of ISA would appear to be the important difference between these two groups of drugs: ISA would, therefore, appear to be demonstrated in man by flattening of the dose-response curves with exercise.

Adrenergic beta-Antagonists↗
PubMed1976

Observations on the efficacy and pharmacokinetics of sotalol after oral administration.

The effects of sotalol after oral administration were measured on the tachycardia induced by strenuous exercise in normal subjects. Plasma sotalol levels were also determined. The oral administration of sotalol (50, 100, 200 and 400 mg) to 6 subjects produced a progressive reduction in the tachycardia induced by severe exercise. This was similar to the effects of 25, 50, 100, 200, 400 and 800 mg given to different subjects. Each increase in sotalol dose produced a successively greater reduction in exercise tachycardia. This did not appear to be maximum even with 800 mg. Oral sotalol was rapidly absorbed and produced peak blood levels in 2 - 3 hours. The plasma levels of sotalol measured 2 hours after the oral administration of 25 to 800 mg showed never more than a six-fold variation between different subject. The half-life of sotalol in plasma was 12.7 +/- SE 1.6 hours. There was a significant correlation between the logarithm of the plasma sotalol concentration and the percentage reduction of exercise heart rate. It is concluded that the oral administration of sotalol either once or twice daily (depending on dose level) will provide satisfactory 24-hour blockade of beta-adrenoceptors.

Administration, Oral↗
PubMed1976

Clinical pharmacologic observations on atenolol, a beta-adrenoceptor blocker.

The effects of oral and intravenous administration of atenolol were studied in healthy volunteers. The oral administration of a series of single doses of atenolol reduced an exercise tachycardia. After a 200-mg dose, the effect on an exercise tachycardia was maximal at 3 hr and declined linearly with time at a rate of approximately 10% per 24 hr. The peak plasma atenolol concentration occurred at 3 hr and thereafter declined exponentially with time with an elimination half-life of 6.36 +/- 0.55 hr: 43 +/- 3.9% of the dose was excreted in the urine within 72 hr. There was a correlation between the reduction in an exercise tachycardia and the logarithm of the corresponding plasma concentration. The intravenous administration of atenolol reduced exercise tachycardia with a significant correlation between effect and plasma concentration. After 50 mg intravenously, 100% of the dose was recovered from the urine, and the clearance was 97.3 ml/min. Comparison of AUC O leads to chi after oral and intravenous administration of 50 mg showed the bioavailability to be 63% after oral drug. Repeated oral administration of atenolol 200 mg daily either as a single dose or in divided 12 hourly doses for 8 days maintained reduction of an exercise tachycardia of at least 24% during the period of drug administration. The plasma elimination half-life, area under the plasma concentration-time curve, and peak plasma concentration after 200 mg atenolol were not changed by chronic dosing for 8 days.

Administration, Oral↗
PubMed1975

Electrical burns of the mouth in children; a method for assessing results.

A retrospective study has been reported of a 15-year experience with electrical burns of the mouth in children. Addtionally, a method has been described by which the surgical results to date can be measured. It seems that the means of initial treatment (excision vs. conservative) does not influence the final results, but rather the extent of injury is probably the crucial factor. Because of a high incidence of significant bleeding from the labial artery, and the concept of early wound excision to diminish late scaring, we continus to favor initial delayed primary excision.

Burns, Electric↗
PubMed1974

The selectivity principle and the question of the bridged structure of the 2-norborynyl cation.

Low exo/endo rate ratios in the solvolysis of certain norbornyl derivatives have been attributed to the involvement of classical (unbridged) 2-norbornyl cations. Consequently, the high exo/endo rate ratio in the parent system, 2-norbornyl arenesulfonates, has been interpreted as involving rate enhancement in the exo isomer arising from sigma-participation. It is pointed out that this treatment involves neglect of the Selectivity Principle. Taking the relative reactivity of cyclopentyl to cyclohexyl as a representative test system, it is pointed out that those reactions which reveal low exo/endo rate ratios in norbornyI also reveal low cyclopentyl/cyclohexyl rate ratios. It is proposed that the low exo/endo rate ratios in norbornyl, observed in the above reactions, arise from the low selectivities of the test reactions. Consequently, the results cannot be utilized to support the argument that low exo/endo rate ratios reflect the absence of sigma-participation and high exo/endo rate ratios reflect the presence of sigma-participation.

Journal Article↗