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Biomedical subjects

L E Black

Publications and source records attributed to L E Black.

11 recordsLinked to original sources
PubMed1994

Cyclic AMP-mediated desensitization of D1 dopamine receptor-coupled adenylyl cyclase in NS20Y neuroblastoma cells.

Cyclic AMP-mediated desensitization of D1 dopamine receptor-coupled adenylyl cyclase was investigated using NS20Y neuroblastoma cells. Pretreatment of the cells for 24 h with 8-(4-chlorophenylthio)-adenosine-3':5'-cyclic monophosphate (CPT-cAMP), a membrane-permeable analog of cAMP, resulted in an approximately 90% reduction of the maximum dopamine-stimulated adenylyl cyclase activity. In addition, there was a twofold reduction in the potency of dopamine for stimulating cAMP production that was not dependent on the concentration of Mg2+ in the assay. These effects of CPT-cAMP pretreatment were time dependent, showing a t1/2 of about 3 h and a maximum reduction after about 8 h. Receptor-binding activity, as measured using the D1-selective antagonist [3H]SCH-23390, also declined following CPT-cAMP pretreatment with a t1/2 of about 5 h and a maximum reduction of about 70% after 20 h. Saturation analysis indicated that the loss in radioligand binding was due to a reduction in maximum binding capacity (Bmax) with no alteration in receptor affinity (KD). The EC50 of CPT-cAMP for producing enzyme desensitization and D1 receptor downregulation was determined to be about 30 microM with a maximal response occurring at 1 mM. These regulatory effects of CPT-cAMP were pharmacologically specific as other analogs of cAMP, such as dibutryl-cAMP, 8-bromo-cAMP, and Sp-cAMPS, were capable of inducing D1 receptor desensitization and downregulation, whereas treatment of the cells with the cAMP antagonist Rp-cAMPS had no effect. Conversely, Rp-cAMPS was capable of blocking the regulatory effects of CPT-cAMP but was apparently without effect in blocking dopamine-induced desensitization.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1994

Regulatory considerations for oligonucleotide drugs: updated recommendations for pharmacology and toxicology studies.

This article describes pharmacology and toxicity studies for oligonucleotide drugs that are recommended for inclusion in the initial Investigational New Drug Application (IND), a first request to use an investigational drug in clinical trials. Recent observations of non-sequence-dependent cardiovascular toxicity and deaths in monkeys following intravenous infusions of phosphorothioates have raised a potential safety concern for oligonucleotide drugs. This concern should be considered by drug sponsors in designing pre-IND nonclinical development programs and Phase I clinical protocols. Pre-IND conduct of pharmacodynamic cardiovascular screening is highly recommended for defining safe clinical dosing regimens for phosphorothioate (and, possibly, other charged-backbone) oligomers. Additionally, drug sponsors are encouraged to (1) conduct research into-the mechanisms responsible for this dose-limiting toxicity, (2) institute liberal publication policies for research conducted under industrial sponsorship, and (3) communicate with reviewing divisions at FDA for updated guidance in this field when planning pre-IND safety studies. Recommendations for nonclinical studies during development of oligonucleotides will be modified as new information regarding the biological properties of oligonucleotides becomes available.

Animals↗
PubMed1993

High-frequency jet ventilation in children with the adult respiratory distress syndrome complicated by pulmonary barotrauma.

High-frequency jet ventilation (HFJV) was used in 29 children with severe ARDS complicated by pulmonary barotrauma (PBT). Treatment with HFJV was begun when PBT was progressing over a 24-h period while receiving conventional ventilation (CV). The mean (+/- SD) age was 0.95 +/- 1.21 years (range, 0.03-4 years). The most common diagnosis was viral pneumonia (n = 17); other diagnoses included aspiration pneumonitis (n = 4), bacterial pneumonia (n = 3), multiple trauma (n = 2), and near-drowning (n = 3). The Bunnell Life-Pulse ventilator was used at a rate of 240/min or 300/min, with inspiratory time of 0.02 sec. Twenty children survived (69%). Survivors and nonsurvivors had equal disease severity prior to HFJV as assessed by ventilator settings, alveolar-to-arterial oxygen tension gradient, oxygenation index, and blood gas values. Survivors had spent significantly less time on conventional ventilation prior to HFJV than nonsurvivors, with a mean (+/- SD) of 3.7 +/- 2.1 days vs 9.6 +/- 4.5 days, respectively (P < 0.05). Survivors underwent an average of 4.4 +/- 3.9 days of HFJV, which supported adequate gas exchange with lower airway pressures, and produced resolution or significant improvement in airleak on chest radiograph. In conclusion, we speculate that the application of HFJV early in the course of severe hypoxemic respiratory failure complicated by airleak, allows the reduction of airway pressures, thereby minimizing pulmonary barotrauma and allowing the lung to recover from the underlying insult. Further controlled evaluation of HFJV in this high risk group of patients is warranted.

Child, Preschool↗
PubMed1993

Regulatory considerations for evaluating the pharmacology and toxicology of antisense drugs.

This article focuses on pharmacology and toxicology data that should be included in an Investigational New Drug Application (IND), a request to use an investigational drug in clinical trials. In general, pharmacology and toxicology testing programs for antisense compounds are held to the same regulatory standards applied to other new therapeutic classes. Biological properties of oligonucleotide therapeutics are mentioned where they may pertain to clinical safety issues. Nonclinical data submitted to the IND should characterize the pharmacology, disposition, and toxicology of a new drug; these data form the basis for clinical risk assessment. Concomitant evaluation of pharmacokinetics allows for better interpretation of in vivo studies and increased accuracy of dose extrapolation to humans. Recommendations for nonclinical drug development will be modified as new information regarding the biological properties of oligonucleotides becomes available.

Animals↗
PubMed1992

Elevated lead levels in a patient with sickle cell disease and inappropriate secretion of antidiuretic hormone.

A five-year-old girl with known sickle cell disease presented with severe hyponatremia and findings compatible with syndrome of inappropriate secretion of antidiuretic hormone (SIADH). She was found to have lead levels in the Class III category. By exclusion, we postulated that the SIADH was in some way related to the high lead levels, since this was the only abnormality the patient exhibited. The toxic lead levels and the elevated vasopressin levels rapidly responded to dimercaprol and calcium EDTA chelation therapy.

Anemia, Sickle Cell↗
PubMed1991

N-(p-isothiocyanatophenethyl)spiperone, a selective and irreversible antagonist of D2 dopamine receptors in brain.

N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ), an irreversible and nonselective protein-modifying reagent, has been used extensively in studies involving inactivation of receptors. Here, we present N-(p-isothiocyanatophenethyl)spiperone (NIPS), a novel and highly selective irreversible inactivator of D2 but not D1 receptors. In in vitro studies, NIPS exhibited an apparent Ki of 10 nM for [3H]methylspiperone binding to D2 receptors in rat striatum. Preincubation of the striatal membranes with NIPS followed by extensive washing resulted in up to an 80% reduction of the D2 receptor maximum binding (Bmax). Coincubation with the D2 receptor antagonist domperidone could protect against this reduction. NIPS was additionally shown to irreversibly inactivate D2 receptor binding activity in cultured cells expressing the D2 receptor protein. In in vivo administration studies, using [3H]SCH 23390 and [3H]spiperone to assay D1 and D2 receptors in vitro, 24 hr after injection (s.c.) with 5 to 40 mg/kg of NIPS D2 receptor, Bmax was decreased by 58 to 76%, without a change in D2 receptor affinity. In contrast, there was no effect on D1 receptor Bmax or affinity. There was also a small (24%) reduction in frontal cortex 5-hydroxytryptamine2 receptors by 20 mg/kg of NIPS. However, there was no effect on alpha-1 or alpha-2 adrenergic receptors in the frontal cortex, or on muscarinic cholinergic or 5-hydroxytryptamine1A receptors in the hippocampus. After single doses of either 20 mg/kg of NIPS or 10 mg/kg of EEDQ, the D2 receptor recovery rate was much slower after NIPS (half-time of receptor recovery = 170 hr) than after EEDQ (half-time of receptor recovery = 76.7 hr).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗
PubMed1991

Agonist-induced desensitization of D2 dopamine receptors in human Y-79 retinoblastoma cells.

Y-79 human retinoblastoma cells can be induced to express significant quantities of functional D2 dopamine receptors after attachment and differentiation with sodium butyrate. In membranes prepared from differentiated Y-79 cells, the D2 dopaminergic antagonist [3H] methylspiperone exhibits a KD of 77 pm and a Bmax of 60 fmol/mg of protein, whereas the antagonist [125I]iodosulpride reveals a KD of 0.77 nM and a Bmax of 40 fmol/mg of protein. Dopamine also induces a pharmacologically specific, pertussis toxin-sensitive, dose-dependent inhibition of forskolin-stimulated adenylyl cyclase activity, with an EC50 of 2 microM and a maximal response at 100 microM (approximately 50% enzyme inhibition). Pretreatment of the cells with dopamine results in a diminution in the subsequent ability of dopamine to inhibit adenylyl cyclase activity. This effect is time dependent, reaching maximal desensitization after approximately 24 hr. The dopamine dose-response curve for inducing desensitization exhibits an EC50 of approximately 2-3 microM and a maximal response at approximately 0.1-1 mM, similar to that for inhibiting adenylyl cyclase activity. After maximal desensitization, the EC50 for dopamine-induced inhibition of adenylyl cyclase activity is increased greater than 20 fold (lower affinity) and the maximum inhibition is decreased to approximately 15%, representing an approximately 70% desensitization. The agonist-induced desensitization is pharmacologically specific, inasmuch as preincubation of the cells with the dopaminergic agonists epinine and (+-)-2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene or the D2-selective agonist N-0434 also results in desensitization of dopamine-induced inhibition of enzyme activity, whereas preincubation with the D1-selective agonist SKF-38393 or with the nondopaminergic agonists isoproterenol and serotonin results in little or no desensitization. Preincubation of the cells with dopamine also promotes a time-dependent increase (approximately 3-fold) in the KD for [3H]methylspiperone, with no change in its Bmax. In contrast, after dopamine preincubation, the KD for [125I]iodosulpride is unchanged, whereas its Bmax is reduced by approximately 50% upon maximum desensitization. In addition, agonist pretreatment promotes a functional uncoupling of the D2 receptor, as suggested by a loss of high affinity agonist binding observed in radioligand competition binding assays after desensitization. Upon removal of agonist, the cellular D2 receptor binding activity and functional response recover to control levels within a 24-hr period. These results suggest that prolonged exposure of cells to dopaminergic agonists initiates a desensitization process involving a functional uncoupling of the D2 dopamine receptor as well as a loss of its ligand binding activity.

Adenylate Cyclase Toxin↗
PubMed1989

Prognostic variables in osteosarcoma: a multi-institutional study.

This is a report of a multi-institutional study of all patients with osteosarcoma who were seen at 13 comprehensive cancer centers from July 1, 1977, to December 31, 1982. Follow-up extended to 9 years; a minimum of 3 years was obtained for greater than 90% of the patients. All patients with osteosarcoma were considered, but only those with tissue confirmation who had had at least part of their first course of treatment at one of the 13 institutions were included. There were 543 patients. In a search for prognostic indicators, 38 patient characteristics, three treatment categories, and an institutional variable were studied. A combination of nine of these constituted the best indicator of survival. They were morphology (two parts), site of primary cancer (two parts), spread of tumor, grade and size of tumor, duration of symptoms, weight loss of greater than 4.5 kg (10 lb), swelling at primary site, and lytic appearance. Unexpectedly, treatment was not one of the indicators of survival. A prognostic score was developed in which the coefficients were obtained from the Cox regression (step-down) method. Each patient had a score (S) and an observed survival time that together provided the expected risk of death for that patient. Although this was not a randomized study, treatments were compared before and after adjusting for characteristics identified as prognostic. Three treatments differed little: surgery alone, surgery plus chemotherapy and/or radiotherapy, and chemotherapy and/or radiotherapy followed in 1-4 months by surgery. Patients with amputations and those with resections had similar death rates, but the observed progression rates differed widely. However, when the rates were adjusted for prognostic characteristics, the difference disappeared. Complete surgery (if osteosarcoma existed within surgical margins) was no better than incomplete surgery (if osteosarcoma existed beyond surgical margins) with respect to death but, as would be expected, complete surgery was much better with respect to disease progression.

Follow-Up Studies↗
PubMed1981

Familial cancer in an oncology clinic.

Knowledge of cancer genetics provides the physician with a powerful tool for the recognition of patients who might profit from highly targeted cancer surveillance/management programs. Family history was evaluated by registered nurses on 565 consecutively ascertained patients with verified cancer from Creighton's Oncology Clinic. This initial assessment yielded 199 (35.5%) families with two more family members with cancer (all sites) within an informative nuclear component, which constituted parents, grandparents, aunts/uncles, siblings, and children. One or more of the operational criteria for cancer familiality, namely vertical transmission of cancer, bilaterality, and/or multiple primaries, early age of onset, and three or more site specific cancers, were found on physician review in 171 (30.5%) of the families. This group was referred for comprehensive cancer genetic evaluation consisting of pedigree extension and tumor verification through all second degree, and when possible, third degree relatives. It was determined that approximately 4% of the total clinic population demonstrated findings compatible with hereditary cancer syndromes. Its universal extension in clinical practice is advocated because of the potential yield from meticulous surveillance for cancer of highly targeted organs in such high-risk kindreds, as well as the economy and general case of obtaining detailed family history by registered nurses. The physician is able, therefore, to devote his primary effort toward pedigree analysis and syndrome identification.

Adolescent↗