Pharmacokinetics and metabolism of the pharmacologically active 4'-hydroxylated metabolite of propranolol in the dog

The disposition of 4'-hydroxypropranolol (HOP) was determined after iv administration to dogs (2 mg/kg; N = 5) and the pharmacokinetic parameters were calculated from plasma measurements. The clearance of HOP, 66 +/- 6 ml/min/kg (mean +/- SE), was considerably higher than that of propranolol previously determined, suggesting extrahepatic as well as hepatic clearance of HOP. The plasma half-life of HOP, 77 +/- 6 min, was shorter than that of propranolol. Although HOP is considerably less lipophilic than propranolol, its volume of distribution, 6.4 +/- 0.8 liter/kg, surprisingly, was larger. Like propranolol, HOP appeared to be cleared entirely by metabolism. Whereas propranolol is metabolized mainly by oxidation, HOP was metabolized to sulfate (HOPS) and glucuronic acid (HOPG) conjugates. The plasma half-lives of these conjugates were 2 to 3 times longer than for HOP, reflecting a slow, continuous formation from HOP. This was established for HOPS by iv administration of synthetic HOPS. Morover, after HOP administration both formation and renal clearance of HOPS were stereoselective in favor of the R-enantiomer. In summary, the main conclusion of this study is that the large volume of distribution as well as high clearance through sulfation and glucuronidation may explain the low plasma HOP levels observed during propranolol therapy.     

Actions of acetylcholine and GABA on spontaneous contractions of the filariid, Dipetalonema viteae.

1. Isotonic contractions were recorded from the filarial nematode, Dipetalonema viteae (Acanthocheilonema viteae), in an isolated tissue chamber. 2. Nicotine (10(-6) M) and pilocarpine (10(-5) M) increased the spontaneous contractions in the intact filariid, but acetylcholine (ACh, 10(-4) M) and muscarine (10(-5) M) were inactive. 3. When ACh was applied to an opened D. viteae, it was 10,000 times more potent. This indicates that the cuticle is an effective barrier to the penetration of ACh to the muscle cells. 4. The effects of ACh on the opened D. viteae were not affected by hexamethonium (10(-3) M) or atropine (10(-5) M) and were only partially reduced by (+)-tubocurarine (10(-4) M). 5. gamma-Aminobutyric acid (GABA, 10(-3) M) reduced the spontaneous activity of the intact D. viteae; however, the effect of GABA had a slow onset and recovery. Muscimol (10(-5) M) was more potent than GABA and had a more rapid onset and recovery. 6. GABA was 1,000 times more potent on the opened D. viteae than on the intact D. viteae. Baclofen (10(-3) M) was inactive on both preparations. 7. The effect of GABA was not antagonized by bicuculline (10(-4) M), picrotoxin (10(-5) M or penicillin G (10(-3) M). 8. It is concluded that the filariid cuticle acts like a lipid structure and blocks the penetration of polar substances, such as ACh and GABA. Also, due to the lack of efficacy of the ACh and GABA antagonists, it was concluded that the nematode receptors are somewhat different from the mammalian ACh and GABA receptors.     

A phase II study of sulofenur,a novel sulfonylurea,in recurrent epithelial ovarian cancer

Summary A total of 16 patients with recurrent epithelial ovarian cancer were treated with sulofenur (LY 186641), a novel oral sulfonylurea. All subjects had received previous chemotherapy. Anaemia occurred in all 16 patients, 14 of whom required a blood transfusion, and 2/16 patients received methylene blue for breathlessness due to methaemaglobinaemia. Treatment was discontinued in 2/16 cases due to rising liver enzyme values, which reverted to normal on cessation of the drug. There was no nausea or alopecia. Only two minor responses were seen. Plasma drug levels were insufficient to result in antitumour activity as extrapolated from animal data. Further studies that attempt to increase the bioavailability and improve the therapeutic index are warranted.     

Emergency aortic valve replacement for critical aortic stenosis

Objective: To demonstrate that emergency aortic valve replacement can be successfully performed in patients with critical aortic stenosis and reduced left ventricular function even in cardiogenic shock with associated severe multiple organ failure. Design: Retrospective, consecutive case series. Setting: Multidisciplinary intensive care unit of a tertiary care university hospital. Patients: Five patients admitted to the intensive care unit with critical aortic stenosis (aortic valve area 0.56 ± 0.13 cm²) and greatly reduced left ventricular ejection fraction (20 ± 3 %) in prolonged cardiogenic shock and associated multiple organ failure (Multiple organ failure score 6.8 ± 0.5; Acute Physiology, Age, and Chronic Health Evaluation III score 91 ± 27). Intervention: Emergency aortic valve replacement. Results: All patients survived with full recovery of organ function. At follow-up (18 ± 10 months) all patients were in New York Heart Association functional class I or II with improvement of left ventricular ejection fraction to 48 ± 25 %. Conclusions: This excellent outcome suggests that emergency aortic valve replacement should be strongly considered in patients with critical aortic stenosis even in cardiogenic shock and multiple organ failure.     

Linkage of the MHC to familial multiple sclerosis suggests genetic heterogeneity. The Multiple Sclerosis Genetics Group

Multiple sclerosis (MS) is a demyelinating autoimmune disease of the central nervous system. While its etiology is not well understood, genetic factors are clearly involved. Until recently, most genetic studies in MS have been association studies using the case-control design testing specific candidate genes and studying only sporadic cases. The only consistently replicated finding has been an association with the HLA-DR2 allele within the major histocompatibility complex (MHC) on chromosome 6. Using the genetic linkage design, however, evidence for and against linkage of the MHC to MS has been found, fostering suggestions that sporadic and familial MS have different etiologies. Most recently, two of four genomic screens demonstrated linkage to the MHC, although specific allelic associations were not tested. Here, a dataset of 98 multiplex families was studied to test for an association to the HLA-DR2 allele in familial MS and to determine if genetic linkage to the MHC was due solely to such an association. Three highly polymorphic markers (HLA-DR, D6S273 and TNFbeta) in the MHC demonstrated strong genetic linkage (parametric lod scores of 4.60, 2.20 and 1.24, respectively) and a specific association with the HLA-DR2 allele was confirmed (TDT; P < 0.001). Stratifying the results by HLA-DR2 status showed that the linkage results were limited to families segregating HLA-DR2 alleles. These results demonstrate that genetic linkage to the MHC can be explained by the HLA-DR2 allelic association. They also indicate that sporadic and familial MS share a common genetic susceptibility. In addition, preliminary calculations suggest that the MHC explains between 17 and 62% of the genetic etiology of MS. This heterogeneity is also supported by the minority of families showing no linkage or association with loci within the MHC.      

Sclerotomal origin of smooth muscle cells in the wall of the avian dorsal aorta.

The dorsal aorta is the earliest formed intraembryonic blood vessel. It is composed of an inner lining consisting of endothelial cells and an outer wall consisting of smooth muscle cells (SMCs) and fibrocytes. Aortic SMCs have been suggested to arise from several developmental lineages. Cephalic neural crest provides SMCs of the proximal part of the aorta, and SMCs of the distal part are derived from the paraxial mesoderm. Here, we show by using quail-chick chimerization that in the avian embryo, SMCs in the wall of the dorsal aorta at trunk level arise from the sclerotome. Our findings indicate a two-step process of aortic wall formation. First, non-paraxial mesoderm-derived mural cells accumulate at the floor of the aorta. We refer to these cells as primary SMCs. Second, SMCs from the sclerotome are recruited to the roof and sides of the aorta, eventually replacing the primary SMCs in the aortic floor.     

Distribution and migration of angiogenic cells from grafted avascular intraembryonic mesoderm

Summary The hemangiogenic potencies of initially avascular intra-embryonic mesoderm were studied in chick and quail embryos and in chick-quail chimeras. The prechordal mesoderm, primitive streak and primitive node of quail embryos were heterospecifically grafted into limb buds of chick embryos. Hemangiopoietic quail cells in the host limb were detected by immunohistological staining with the monoclonal anti-MB-1 antibody after 3–6 days of re-incubation. The antibody is specifically directed against quail hemangiopoietic cells and their derivatives. Quail endothelial cells were found in pure quail and in chimeric vessels, inside as well as outside the graft. The main artery of the limb and the vessels inside the graft were connected by chimeric arteries. Proximal to the graft, quail endothelial cells were located predominantly within the lining of the main artery, while distally they were found mainly in the veins and the marginal sinus. The results show that, as early as stage 3 (according to Hamburger and Hamilton 1951, HH) all parts of the avascular intraembryonic mesoderm tested, give rise to endothelial cells. Both mechanisms, angiogenesis and vasculogenesis, contribute to the vascularization of the limb. Immunocytological and scanning electron microscopic studies indicate that centrifugal and centripetal migration of angiogenic cells occurs outside the vessels as well as on the inner surface of the endothelium.Supported by the Deutsche Forschungsgemeinschaft (CH 44/9-1)