The relative merits of cromolyn sodium and high-dose theophylline therapy in childhood asthma

The use of cromolyn sodium (SCG) and high-dose theophylline (HDT) in the treatment of chronic perennial asthma in children is reviewed. It is noted that the regimens are only suitable for children with persistent symptoms uncontrolled by simpler forms of treatment. The methods of administration and dosage based on pharmacologic data are considered, and the potential importance of long-acting theophylline and nebulized cromolyn preparations is noted. Short-term studies have confirmed the efficacy of both drugs, and a comparative study showed little difference between them. Long-term studies of SCG have demonstrated its value to some 66% of children without serious side effects. No formal long-term studies have been carried out on HDT. Side effects from theophylline can often be eliminated by careful control of blood levels. From published evidence, neither SCG nor HDT is effective in steroid-dependent asthmatic children, and they contribute little, if anything, to management in such cases. The difference in cost of the drugs is small when all factors are considered, and either regimen is justified by the saving in medical expenses when used for carefully selected patients.     

The immunophilin ligand FK506, but not the P38 kinase inhibitor SB203580, improves function of adult rat muscle reinnervated from transplants of embryonic neurons

Injury to the adult CNS often involves death of motoneurons, resulting in the paralysis and progressive atrophy of muscle. There is no effective therapy to replace motoneurons in the CNS. Our strategy to replace neurons and to rescue denervated muscles is to transplant dissociated embryonic day 14-15 (E14-15) ventral spinal cord cells into the distal stump of a peripheral nerve near the denervated muscles. Here, we test whether long-term delivery of two pharmacological inhibitors to denervated muscle, FK506 or SB203580, enhances reinnervation of muscle from embryonic cells transplanted in the tibial nerve of adult Fischer rats. FK506, SB203580 (2.5 mg/kg) or saline was delivered under the fascia of the medial gastrocnemius muscle for 4 weeks, beginning when muscles were denervated by section of the sciatic nerve. After 1 week of nerve degeneration, one million E14-15 ventral spinal cord cells were transplanted into the distal tibial nerve stump of each rat in the three treatment groups. Ten weeks later, all cell transplants had neuron-specific nuclear protein (NeuN) positive neurons. Neuron survival and axon regeneration were similar across treatments. An average (+/-S.E.) of 210+/-66, 100+/-36 and 176+/-58 myelinated axons grew distally from the cell transplants of rats with muscles treated with FK506, SB203580 or saline, respectively. Regenerating axons in muscles of all three treatments groups were detected with antibodies against phosphorylated neurofilaments and synaptophysin, and motor end plates were labeled with alpha-bungarotoxin. Muscles of rats that received transplants of media only had no axon growth, indicating that the muscles were denervated. The mean muscle fiber areas of rats that received cell transplants and had long-term delivery of FK506, SB203580 or saline to muscles were significantly larger than those of denervated muscle fibers. Thus, cell transplantation reduced muscle atrophy. Transplantation of embryonic cells also resulted in functional muscle reinnervation. Electromyographic activity and force were evoked from >90% of the muscles of rats with cell transplants, but not from denervated muscles. FK506-treated muscles were significantly more fatigue resistant than naive control muscles. FK506-treated muscles also had significantly stronger motor units than those in SB203580 or saline-treated muscles. These data suggest that a pathway regulated by FK506 improves the function of muscles reinnervated by embryonic neurons placed in peripheral nerve.     

Characterization of the epitope recognized by a mAb that reacts differentially with murine suppressor T cells

Although reliable antibodies are available that distinguishhuman suppressor T (T_s) cells from CTL and other T cells, feware available for murine T_s cells. We have developed a mAb (984D4.6.5)that, in the presence of complement, depletes alloantigen-specificT_s cells but not CTL. This antibody recognizes activated TT_scells but not their precursors. In these studies, flow cytometricanalysis demonstrates that 984D4.6.5 reacts with several T_scell hybridomas, cloned T_h cell lines and WEHI-3 (a myelomonocytictumor cell line). Reactivity was not detected with BW5147, T_hcell hybridomas, cloned T_h cells, CTL lines and hybridomas,B cell lines, thymocytes, splenocytes, bone marrow cells nora variety of tumor cells. Among 984D4.6.5 positive lines, expressionis heterogeneous and the number of cells expressing high levelsof the epitope is increased when the hybridomas are maintainedat a relatively high cell density. Neuriminidase and pronasedeplete the epitope recognized by mAb 984D4.6.5. Protein synthesisand glycosylation inhibitors also reduce expression of thisepitope. These observations suggest that the epitope recognizedby 984D4.6.5 is a carbohydrate linked to a polypeptide. Thisantibody was tested by ELISA for binding to a large panel ofcarbohydrates and glycollpids coupled to BSA. The only one thatbound 984D4.6.5 was LS tetrasaccharide c (NeuNAc2-6Galpß1-4GIcNAcß1-3GaIß1-4Glc),an O-linked carbohydrate. Comparative analysis shows that boththe sequence and the linkage of these sugars are essential tothe reactivity with the 984D4.6.5 antibody. This epitope isexpressed by a glycoprotein of-200 kDa, as shown by Westernblots. The identity of this glycoprotein remains to be determined,but indirect evidence suggests that it is not CD45.     

Ca-EGTA affects the relationship between [Ca2+] and tension in α-toxin permeabilized rat anococcygeus smooth muscle

Summary The relationship between calcium concentration ([Ca²⁺]) and force in smooth muscle can be studied by permeabilizing the sarcolemma and bathing the preparation in a mock intracellular solution. Normally [Ca²⁺] is set in these solutions using the Ca²⁺ chelator EGTA in the concentration range of 4–10 mm. This study shows that lowering total EGTA concentration ([EGTA]_t) below 10 mm depresses Ca²⁺-activated force generated in 0.1 m Ca²⁺. The observed threshold for the effect of EGTA_t is 0.2 mm, and the effect is maximal at approximately 10 mm. BAPTA, another Ca²⁺ chelator, also produces this effect. Tension production in smooth muscle is controlled by acto-myosin interaction. This in turn is mediated by the relative activities of myosin light chain kinase (MLCK) and phosphatase (MLCP). Inhibiting MLCP with Microcystin LR (10 m), an increase [EGTA_t] from 0.2 mm to 10 mm still enhanced force. This suggests that EGTA promotes phosphorylation of myosin by the activation of MLCK and not by inhibition of MLCP.     

Studies on the stability of trimelamol, a carbinolamine-containing antitumor drug

The stability of trimelamol (N2,N4,N6-trimethylol-N2,N4,N6-trimethylmelamine) a synthetic carbinolamine-containing antitumor drug, has been studied. Two major degradation pathways have been characterized and a unified mechanism proposed to rationalize the chemistry involved. One degradation pathway involves the consecutive loss of hydroxymethylene units by elimination of formaldehyde until the parent trimethylmelamine (4) results. An HPLC method was used to obtain kinetic data for the loss of trimelamol and to monitor the order of appearance of three degradation products. This pathway was shown to follow first-order kinetics at all pH values studied at both 18 and 37 degrees C. The second pathway involves the coupling of two trimelamol molecules via a methylene bridge to form bis(trimelamol) (6) which had been previously referred to in the literature as a "polymer". This reaction is acid catalyzed and temperature dependent. Bis(trimelamol) is virtually water insoluble and adheres strongly to glass surfaces. Finally, t1/2 values have been determined for trimelamol in aqueous solution at different temperatures, and the kinetics of formation of degradation products has been studied over a period of 30 h under a variety of conditions of pH and temperature. The data reported here are relevant to both the formulation and clinical administration of trimelamol, and may contribute to an understanding of mechanism of action and future analogue development studies.     

A chromatographic and spectroscopic study of photodegraded metronidazole in aqueous solution

Preparative reversed-phase HPLC has been used to isolate a yellow photodegradation (2) product from aqueous metronidazole (1) solutions buffered with citrate:phosphate. Compound 2 can be further degraded into colorless materials by light, heat, or the addition of the nonaqueous solvents. These products have been characterized by UV, IR, proton NMR, mass spectroscopy, and melting point determination. It is proposed that the initial yellow degradation product (2) is an "excimer ion-pair" formed by the stabilization of 1 in its first electronic excited state by the citrate molecule.