Identification of MK-944a: a second clinical candidate from the hydroxylaminepentanamide isostere series of HIV protease inhibitors.

Recent results from human clinical trials have established the critical role of HIV protease inhibitors in the treatment of acquired immune-deficiency syndrome (AIDS). However, the emergence of viral resistance, demanding treatment protocols, and adverse side effects have exposed the urgent need for a second generation of HIV protease inhibitors. The continued exploration of our hydroxylaminepentanamide (HAPA) transition-state isostere series of HIV protease inhibitors, which initially resulted in the identification of Crixivan (indinavir sulfate, MK-639, L-735,524), has now yielded MK-944a (L-756,423). This compound is potent, is selective, and competitively inhibits HIV-1 PR with a K(i) value of 0.049 nM. It stops the spread of the HIV(IIIb)-infected MT4 lymphoid cells at 25.0-50.0 nM, even in the presence of alpha(1) acid glycoprotein, human serum albumin, normal human serum, or fetal bovine serum. MK-944a has a longer half-life in several animal models (rats, dogs, and monkeys) than indinavir sulfate and is currently in advanced human clinical trials.

Mercaptopyridine-N-oxide, an NADH-fumarate reductase inhibitor, blocks Trypanosoma cruzi growth in culture and in infected myoblasts.

The enzyme NADH-fumarate reductase is not found in mammalian cells but it is present in several parasitic protozoa including Trypanosoma cruzi, the parasite that causes Chagas' disease. This study shows that the drug 2-mercaptopyridine-N-oxide (MPNO) inhibits NADH-fumarate reductase purified from T. cruzi (ID50 = 35 microM). When added to intact cells, MPNO inhibited the growth of T. cruzi epimastigotes in culture (ID50 = 0.08 microM) as well as the infection of mammalian myoblasts by T. cruzi trypomastigotes (ID50 = 20 microM). At a concentration of 2.4 microM, MPNO also inhibited the growth of amastigotes (intracellular dividing forms) in cultured mammalian myoblasts. Supplementation of culture media with 5 mM succinate, the product of fumarate reductase, partially protected against the inhibition of the growth of epimastigotes by MPNO. Moreover, MPNO inhibited the accumulation of succinate in cultures of epimastigotes, as measured by high performance liquid chromatography. Although MPNO may have other intracellular targets in addition to fumarate reductase, these results support the hypothesis that compounds which inhibit the enzyme fumarate reductase may be potential chemotherapeutic agents against Chagas' disease.

Proposal for experimental studies to evaluate sodium hypochlorite dialysate in retroviral treatment.

Sodium hypochlorite (NaOCl) is widely used to inactivate retroviruses topically and on environmental surfaces. This proposal establishes the thesis that sodium hypochlorite and its related oxygen free radicals can be administered in minute quantities in vivo to achieve a reduction in retroviral titer within the infected individual. Published reports of animal studies and accidental sodium hypochlorite infusion in much greater concentrations have indicated that the protein depletion and oxidation of sulfhydryl compounds is reversible and possibly preventable by administration of disulfide reducing agents. Various methods of infusion can include the ex vivo retroviral inactivation of plasma utilizing extracorporeal circulation through a continuous centrifugal plasma separator. The utilization of infusion of low-concentration sodium hypochlorite dialysate for retroviral inactivation merits immediate experimental study. Chlorinated tap-water and table salt ingestion must also be among the environmental factors studied for correlation to HIV infection.

Arteriovenous malformation in the pregnant patient: a case study.

Subarachnoid hemorrhage (SAH) due to ruptured arteriovenous malformation (AVM) or aneurysm accounts for 4.4% of all maternal deaths. It is the third most common nonobstetric cause of maternal death. Significant differences, such as timing of the initial bleed and rebleeding, exist between aneurysmal and AVM related SAH. Increased risk of AVM related SAH appears to correlate with the augmented cardiac output of pregnancy, as well as with other coagulation, hemodynamic and endocrinological changes. These changes usually occur between 20 weeks gestation and 6 weeks postpartum. All suspicious neurological signs and symptoms in the gravid patient should be thoroughly evaluated. Although the nursing care of the pregnant patient with an AVM is similar to that of nonpregnant patients, there are specific clinical observations that are relevant to these patients.

Kisspeptin-10 is a potent stimulator of LH and increases pulse frequency in men.

CONTEXT: Kisspeptins stimulate GnRH and thus gonadotropin secretion. Kisspeptin-10 is the minimal kisspeptin sequence with full intrinsic bioactivity, but it has not been studied in man. OBJECTIVE: We investigated our hypothesis that kisspeptin-10 increases GnRH and thus LH pulse frequency. DESIGN AND PARTICIPANTS: The dose response of kisspeptin-10 was investigated by administering iv bolus doses (0.01-3.0 µg/kg) and vehicle to healthy men. Effects on LH pulse frequency and size were determined by deconvolution analysis during infusion of kisspeptin-10 for up to 22.5 h. RESULTS: Intravenous bolus kisspeptin-10 resulted in a rapid and dose-dependent rise in serum LH concentration, with maximal stimulation at 1 µg/kg (4.1 ± 0.4 to 12.4 ± 1.7 IU/liter at 30 min, P < 0.001, n = 6). Administration of 3 µg/kg elicited a reduced response vs. 1 µg/kg (P < 0.05). Infusion of kisspeptin-10 at 4 µg/kg · h for 22.5 h elicited an increase in LH from a mean of 5.4 ± 0.7 to 20.8 ± 4.9 IU/liter (n = 4; P < 0.05) and serum testosterone increased from 16.6 ± 2.4 to 24.0 ± 2.5 nmol/liter (P < 0.001). LH pulses were obscured at this high rate of secretion, but a lower dose infusion of kisspeptin-10 (1.5 µg/kg · h) increased mean LH from 5.2 ± 0.8 to 14.1 ± 1.7 IU/liter (n = 4; P < 0.01) and increased LH pulse frequency from 0.7 ± 0.1 to 1.0 ± 0.2 pulses/h (P < 0.05) and secretory burst mass from 3.9 ± 0.4 to 12.8 ± 2.6 IU/liter (P < 0.05). CONCLUSIONS: Kisspeptin-10 boluses potently evoke LH secretion in men, and continuous infusion increases testosterone, LH pulse frequency, and pulse size. Kisspeptin analogues have therapeutic potential as regulators of LH and thus testosterone secretion.

Attempted dose intensified cyclophosphamide, etoposide, and granulocyte colony-stimulating factor for treatment of malignant astrocytoma.

Patients with malignant astrocytoma continue to respond poorly to chemotherapy and have a dismal prognosis. Cyclophosphamide (CTX) and etoposide demonstrate activity against malignant astrocytoma at standard dosages, with bone marrow suppression as the limiting toxicity. In order to allow dose intensification, minimize leukopenia, and improve efficacy granulocyte colony-stimulating factor (G-CSF) was used in combination with CTX and etoposide. The protocol consisted of CTX (2 mg/m2/d, days 1, 2), etoposide (200-300 mg/m2/d, days 1-3), and G-CSF (5-10 micrograms/d subcutaneously, days 4-18), every 4 weeks. Nine evaluable patients (7 glioblastoma multiforme, 2 anaplastic astrocytoma) were treated, ranging in age from 26-67 (mean 41). One of 9 patients responded (11%) with a partial response (13+ months), 3 had stable disease (33%; 8, 5, 2.5 months), and 5 had progressive disease (3, 2.5, 2, 1.5, 1 months). The median time to progression for responders was 6.5 months, while overall it was 2.5 months. Overall median survival was only 7.0 months. Toxicity was frequent and severe, typically delaying treatment cycles. The most common complications were severe myeolosuppression (9), sepsis (8), rash (6), urinary infection (5), and anorexia (5). Treatment delays caused by infections and other complications occurred often, abrogating the intended dose intensification. The received dose intensity (DI) for CTX was 400-425 mg/m2/week (relative DI 0.41), while for etoposide it was 75 mg/m2/week (relative DI 0.42). In summary, as used in this protocol, dose intensive chemotherapy with CTX, etoposide, and G-CSF does not improve efficacy over standard regimens and results in excessive toxicity.

Making planned and unplanned role transitions.

Changes in organizations mean planned and unplanned role transitions for nurse administrators and managers. Keeping abreast of trends engaging in activities that promote professional growth, assessing work habits, maintaining job interviewing skills, and reviewing and updating resumes are essential to prepare for role changes. When unplanned changes occur because one is fired or a position is abolished, one has to organize personal needs, cope with the job loss, look for a job, and assume a new role. The authors discuss strategies that can be used personally or with others to facilitate job change.

Co-expression in vertebrate tissues and cell lines of multiple inositol 1,4,5-trisphosphate (InsP3) receptors with distinct affinities for InsP3.

Inositol 1,4,5-trisphosphate (InsP3) is a ubiquitous second messenger in eukaryotic cells that triggers Ca2+ release from intracellular stores. Three types of InsP3 receptors have been identified in mammals. The three receptor types are encoded by homologous genes and are structurally similar, suggesting two alternative hypotheses about the biological significance of multiple InsP3 receptors: (a) the different InsP3 receptors could have similar functions as InsP3-gated Ca2+ channels, and the presence of multiple genes could then serve as a mechanism to allow tissue-specific differential expression of receptors; or (b) the different receptors are co-expressed in cells but have distinct biological roles in these cells. To test these hypothesis, we have investigated the similarities and differences between the expression, alternative splicing, and ligand binding of different receptors. Our results demonstrate co-expression of different InsP3 receptors in almost all tissues and cell lines tested. Although all receptor types exhibit a similar specificity for inositol phosphates, the different receptors have different affinities for InsP3, with a relative order of affinities of type II > type I > type III. These findings suggest that the presence of multiple InsP3-sensitive Ca2+ pools with differential responsiveness to InsP3 may be a general property of all cells mediated by the presence of multiple types of InsP3 receptors.

Structure and expression of the rat inositol 1,4,5-trisphosphate receptor.

The complete primary structure of the inositol 1,4,5-trisphosphate receptor from rat brain was elucidated using a series of overlapping cDNA clones. Two different sets of clones that either contain or lack a 45-nucleotide sequence in the amino-terminal third of the protein were isolated, suggesting a differential splicing event that results in the biosynthesis of either a 2734- or 2749-amino acid receptor protein. Hydrophobicity analysis demonstrates the presence of a cluster of hydrophobic sequences in the carboxyl-terminal third of the protein that probably comprise eight transmembrane regions and that may form the calcium channel intrinsic to the receptor. The receptor was universally expressed at low levels in all tissues and cultured cells tested. Transfection of a full-length expression construct of the inositol 1,4,5-trisphosphate receptor into COS cells resulted in the biosynthesis of a 260-kDa protein that bound inositol 1,4,5-trisphosphate and formed high molecular weight complexes similar to the native receptor as analyzed by sucrose gradient centrifugations. On the other hand, the protein product synthesized by a mutant receptor construct in which the amino-terminal 418 amino acids were deleted failed to bind inositol 1,4,5-trisphosphate. The mutant receptor still formed high molecular weight complexes, suggesting that it folded normally and that the amino-terminal sequences of the receptor are part of the ligand binding domain.

Spinal cord tumors: review of etiology, diagnosis, and multidisciplinary approach to treatment.

Spinal cord tumors (SCT) are a diverse group of uncommon neoplasms that develop from tissues in and around the spinal canal. They often have an indolent onset and progression of signs and symptoms, which may include back pain, extremity weakness, sensory alterations, and bowel or bladder incontinence. The most common SCTs are located in the extramedullary space and include meningiomas and neurofibromas. Intramedullary SCTs, for example ependymomas and astrocytomas, occur less frequently. The most useful screening test for diagnosis of a SCT is enhanced magnetic resonance imaging; myelography and computed tomography also can be helpful. The majority of SCTs are amenable to surgical therapy and can be partially or completely resected. Radiation therapy is reserved for incompletely resected low-grade tumors, malignant tumors, and recurrent tumors. The rehabilitative process should be initiated early on following diagnosis, if possible, in patients with neurologic deficits to minimize long-term disability.

Structure of a novel InsP3 receptor.

Inositol 1,4,5-trisphosphate (InsP3) constitutes a major intracellular second messenger that transduces many growth factor and neurotransmitter signals. InsP3 causes the release of Ca2+ from intracellular stores by binding to specific receptors that are coupled to Ca2+ channels. One such receptor from cerebellum has previously been extensively characterized. We have now determined the full structure of a second, novel InsP3 receptor which we refer to as type 2 InsP3 receptor as opposed to the cerebellar type 1 InsP3 receptor. The type 2 InsP3 receptor has the same general structural design as the cerebellar type 1 InsP3 receptor with which it shares 69% sequence identity. Expression of the amino-terminal 1078 amino acids of the type 2 receptor demonstrates high affinity binding of InsP3 to the type 2 receptor with a similar specificity but higher affinity than observed for the type 1 receptor. These results demonstrate the presence of several types of InsP3 receptor in brain and raise the possibility that intracellular Ca2+ signaling may involve multiple pathways with different regulatory properties dependent on different InsP3 receptors.

C6 modification of the pyridinone core of thrombin inhibitor L-374,087 as a means of enhancing its oral absorption.

1 (L-374,087) is a potent, selective, efficacious, and orally bioavailable thrombin inhibitor that contains a core 3-amino-2-pyridinone moiety. Replacement of the C6 pyridinone methyl group of 1 by a propyl group gave 5 (L-375,052), which retained all the excellent properties of 1, and also yielded higher plasma levels after oral dosing in dogs and rats.