Determination of acetazolamide in human serum by enzymatic assay.

Carbonic anhydrase (CA) inhibitors, such as acetazolamide (AZ), formerly used as diuretics, still play a role in the treatment of glaucoma, epilepsy, and altitude sickness. There is now hard evidence from both in vitro and in vivo studies in animals that carbonic anhydrase plays a vital function in bone loss. Acetazolamide blocks bone resorption in these experimental models. We have postulated that acetazolamide has potential for the treatment of human conditions associated with bone loss. In preparation for a clinical trial of acetazolamide's effectiveness in this regard, we developed an enzymatic method for determining the total concentration of acetazolamide in human serum. Acetazolamide is stripped from binding to serum proteins by adding 10(-6) M salicylic acid and adjusting the pH to 2.5, followed by ultrafiltration through a membrane (10 kD cutoff). The latter permits the free acetazolamide to enter the filtrate but retains any carbonic anhydrase (31 kD) which may contaminate the serum from hemolysis. The carbonic anhydrase inhibitory activity in the filtrate, representing the acetazolamide, is determined in a carbonic anhydrase assay using acetazolamide as the standard. Recoveries of acetazolamide added to human serum ranged from 83% to 94% depending on the concentration. Precision, as judged by the coefficient of variation, was 10.5%.     

Response of V beta 8.1+ T cell clones to self Mls-1a: implications for the origin of autoreactive T cells.

Clonal deletion and anergy are two major mechanisms of self-tolerance. However, the molecular mechanisms underlying clonal deletion and anergy, as well as the threshold of TCR affinity/avidity required for these processes, are not known. Expression of the V beta 8.1 TCR correlates with the reactivity of the T cells to the minor lymphocyte stimulating locus-1a (Mls-1a) and T cells expressing this TCR are deleted in the thymus of Mls-1a mice. Similarly, in TCR V beta 8.1 transgenic mice, the number of CD4+CD8-T cells is reduced in Mls-1a mice. However, small numbers of CD4+CD8-T cells remain in the periphery of adult Mls-1a transgenic mice. We have generated T cell clones from TCR V beta 8.1 transgenic mice by stimulation of lymph node T cells with C57BL/6 alloantigens. Interestingly, CD4+CD8-V beta 8.1+ clones isolated from the transgenic mice of Mls-1a background responded to the self-antigen Mls-1a, to which they did not respond in primary assay. Reactive patterns of the clones were compared with clones derived from Mls-1b mice. Proliferation and cytokine production of the clones from Mls-1a mice to the self-antigen Mls-1a were generally reduced when compared with clones from Mls-1b mice. More importantly, T cell clones from Mls-1a mice required more Mls-1a antigen for their activation, and were more susceptible to the inhibitory effects of anti-CD4 antibody on the proliferative responses to Mls-1a than those from Mls-1b mice. These results suggest that the T cell receptor on clones derived from Mls-1a mice have functional but reduced affinity/avidity for self-antigen Mls-1a.     

Pulsed ultrasound Doppler velocimetry in the assessment of microvascular hemodynamics

Pulsed ultrasonic Doppler velocimetry (20 MHz) (PUDVM) has evolved considerably in the last 10 years. Engineering development has resulted in a computer-controlled vessel-scanning instrument whose backscattered frequency shift spectra are analyzed using fast Fourier transforms (FFT). Benchtop and theoretic studies indicate accurate (error less than 5%) velocity and volumetric flow rate measurements in vessels with a lumen diameter as small as 1.2 mm. Clinical application of the PUDVM has provided transcutaneous measurements of blood flow variables in normal human digital arteries. Experimental application to arteries 1.0-1.5 mm has provided information on the hemodynamic effects of topical vasodilators, standard microarteriorrhaphy, variations in microvascular technique, interpositional grafts, and early wound repair. With improving computer capabilities and technical modifications, the PUDVM will be an increasingly important tool in clinical and experimental microsurgery.     

A critical appraisal of the anaesthesia literature

Canadian Journal of Anesthesia/Journal canadien d'anesthésie - Today’s anaesthesia journals are faced with problems in the quality of materials being published. The stature of...     

Physiological properties of conjugated linoleic acid and implications for human health.

Conjugated linoleic acid (CLA) refers to a mixture of positional and geometric dienoic isomers of linoleic acid found naturally in animal products of ruminant sources. Recent interest in CLA research stems from the well-documented anticarcinogenic, antiatherogenic, antidiabetic, and antiobesity properties of CLA in rodents. However, there has been very little published human research on CLA. This review discusses the physiologic properties of CLA and their potential implications for human health.     

Tetrabenazine therapy of pediatric hyperkinetic movement disorders.

Tetrabenazine (TBZ), a presynaptic dopamine depletor and postsynaptic dopamine receptor blocker, is widely used for the treatment of hyperkinetic movement disorders in adults. However, reports of its use in children are limited. We review the efficacy and tolerability of TBZ therapy in 31 children with hyperkinetic movement disorders refractory to other medications. TBZ was effective in reducing the severity of movement disorders resistant to treatment with other medicines. When compared to adult patients, pediatric patients required higher doses. Side effects were similar to the adult population; however, children had a lower incidence of drug-induced Parkinsonism.     

Feeding preferences and attitudes to breastfeeding and its promotion among teenagers in Northern Ireland.

Northern Ireland has one of the lowest breastfeeding initiation rates in the world. Given that attitudes toward infant feeding are formed at an early age and a high rate of teenage pregnancy, it has become necessary to survey attitudes to infant feeding and breastfeeding promotion preferences in teenagers in Northern Ireland. Questionnaires were distributed to teenagers aged 14 to 18 years (n = 419) based in 7 schools selected by type and location throughout Northern Ireland. Attitudes to breastfeeding in public reflected preferred infant-feeding method and were positively influenced by prior exposure to breastfeeding (P = .024). Females were more positive than males both in relation to breastfeeding in public (P = .002) and breastfeeding promotion (P = .003). Recommendations for breastfeeding promotion include specific targeting of young people (both male and female) and enabling contact between teenagers and nursing mothers as much as possible.     

Prenatal diagnosis in diabetic gravidas: utility of ultrasound and maternal serum alpha-fetoprotein screening.

The differences in both the biology of pregnancy and the content of routine care between gravidas with and without diabetes mellitus lead to important differences in the potential utility of both ultrasound examination and maternal serum alpha-fetoprotein (MSAFP) screening. However, both diagnostic methods have become standards of care for these patients, without critical evaluation. This study examines the utility of both ultrasound and MSAFP in diabetic women. Four hundred thirty-two women with diabetes mellitus antedating pregnancy were examined sonographically between 12-23 weeks' gestation. Of these, 393 were also screened with MSAFP determinations. At delivery, 32 of these fetuses were found to have 38 major congenital malformations. All fatal or potentially life-threatening defects had been diagnosed in utero by sonography before 24 weeks' gestation. Ultrasound had a positive predictive value of 90% and a negative predictive value of 97% for identification of major birth defects before 24 weeks' gestation. There were 14 MSAFP values greater than 2.0 multiples of the median, and nine of these patients elected to undergo amniocentesis. Maternal serum alpha-fetoprotein screening had a positive predictive value of 17% and a negative predictive value of 94%. No malformations were detected through MSAFP screening that had not been diagnosed by sonography. No malformations missed sonographically were detected by MSAFP screening, and none of the amniocenteses were helpful diagnostically. We conclude that MSAFP screening is of minimal utility for diagnosing major congenital malformations in a high-risk population examined universally by an experienced sonographer.