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...     

Advanced primary breast cancer: assessment at mammography of response to induction chemotherapy

The response to induction chemotherapy is an important prognostic factor in patients with nonmetastatic, locally advanced breast carcinomas. Assessment at mammography of the response of 60 breast cancers in 59 women was performed between 1974 and 1986. Responses were excellent in 13 tumors, moderate in 34, and poor in 13 (excellent moderate = 78%). Assessment of response of discrete masses in a fatty breast was easiest; assessment of response of tumor areas that were poorly defined-such as a focal area of architectural distortion or mass in dense breast parenchyma-was more difficult. Of 17 patients with excellent pathologic responses-that is, minimal or no residual tumor-15 (88%) had complete responses (no residual tumor) as determined with mammography, physical examination, or both. Mammography provides information complementary to physical examination and is essential in the accurate assessment of the response to chemotherapy of locally advanced breast cancer.     

Lack of interaction between nefazodone and cimetidine: a steady state pharmacokinetic study in humans.

The steady-state pharmacokinetic interaction between nefazodone and cimetidine was evaluated in a three-period crossover study consisting of three treatments of 1 week duration with a 1 week washout between treatments. The 18 healthy, male study subjects received: nefazodone hydrochloride 200 mg twice daily (every 12 h) for 6 days; cimetidine 300 mg four times daily for 6 days; and 200 mg nefazodone hydrochloride twice daily + 300 mg cimetidine four times daily for 6 days. On day 7 of each treatment, only the morning dose was administered. Serial blood samples were collected for pharmacokinetic analysis after drug administration on day 7 of each treatment; blood samples for trough levels (Cmin) to assess attainment of steady state, were also collected just prior to the morning doses on days 2-7 of each study period. Plasma samples were assayed for cimetidine, and nefazodone and its metabolites hydroxynefazodone and m-chlorophenylpiperazine by specific, validated h.p.l.c. methods. Statistical analyses of Cmin data indicated that, regardless of treatment, steady state was achieved for cimetidine by day 2 and for nefazodone and its metabolites by day 3 of multiple dosing, and that there were no significant differences in Cmin levels between treatments. When nefazodone and cimetidine were co-administered for 1 week, no change in steady-state pharmacokinetic parameters for cimetidine, nefazodone or hydroxynefazodone was observed compared with each drug dosed alone.(ABSTRACT TRUNCATED AT 250 WORDS)