Chemoprevention clinical trials.

As part of a program to develop drugs which will delay or prevent cancer in humans, the Chemoprevention Branch, National Cancer Institute, National Institutes of Health, is sponsoring 12 Phase I and 22 Phase II and III clinical trials. Three agent classes are significantly advanced in the trials. These are the retinoids, including 13-cis-retinoic acid, retinol, and 4-hydroxyphenylretinamide (nine studies), beta-carotene (seven studies), and calcium compounds (three studies). In addition, six promising new compounds are in Phase I or Phase II trials. These are: piroxicam, ibuprofen, oltipraz (a dithiolthione), difluoromethylornithine, glycyrrhetinic acid, and N-acetylcysteine. Key concepts related to the development of cancer chemopreventive agents are (1) the need for long-term administration, (2) the need for oral route of administration, (3) the matching of toxic side effects to degree of cancer risk.     

The lysis of Gram-negative Alcaligenes eutrophus by enzymes from Cytophaga

Summary The use of Cytophaga lysing enzymes was investigated for the liberation of poly--hydroxybutyrate (PHB) granules from the Gram-negative bacterium Alcaligenes eutrophus. Complete cell lysis was approached within a 60 minute period. Contrary to previous findings for the lysis of Gram-negative bacteria, prior removal of the outer membrane was not essential for enzymic lysis. The destabilisation of the outer membrane by the removal of divalent cations resulted in no significant improvement in the disruption process.     

How do floater male eastern bluebirds benefit by filling vacancies on territories where females already have young?

When male eastern bluebirds (Sialia sialis) are killed or deserttheir mates, replacement males usually take over the territory.We captured 25 eastern bluebird males and held them in captivityto study the behavior of replacement males and their responseto young already present in the nest. Of 17 replacement males,most courted the females, and 23% of experimental females renested,a proportion not different from that of control females. Noreplacement males were infanticidal, and none fully adoptedthe young. Replacement males spent significantly less time onthe territory and defended it significantly less than controlmales. We discuss breeding options available to a floater maleeastern bluebird and conclude that (1) floater male bluebirdsthat fill territory vacancies benefit by gaining breeding opportunitiesin the current breeding season, and (2) indifference to theyoung is the least costly option for replacement male easternbluebirds.     

Factors affecting recurrent shoot multiplication in in vitro cultures of 17- to 20-year-old douglas fir trees

Summary The effects of sucrose concentration, addition of ammonium nitrate, and exposure to N⁶-benzyl-adenine (BA) on multiplication potential with shoots derived from shoot cultures of 17- to 20-yr-old Douglas fir trees [Pseudotsuga menziesii (Mirb.) Franco] were compared. Each of these conditions, when compared independently, affected recurrent shoot multiplication and influenced shoot development, as measured by the abundance of shoot apices. Sucrose concentration was influential, the use of 25 g · liter⁻¹ providing twice the multiplication obtained with 20 g · liter⁻¹, and 14 × that obtained with the 30 g · liter⁻¹ concentration routinely used (tree 11). Ammonium nitrate usage also improved multiplication, a 2.5 times improvement being obtained after incorporation of 100 mg · liter⁻¹ NH₄NO₃ into the medium (tree 33). Shoot cultures were responsive but relatively sensitive to addition of BA, the best improvement in multiplication (5 times) being obtained with brief exposures to 3 mg · liter⁻¹ BA (tree 11). Although shoot cultures were responsive to the conditions investigated, differences in shoot multiplication and development were not displayed for several weeks. It was not possible therefore to repeat all the treatments with more than one genotype; however, when this was possible a genotype-dependent variation in response was evident.     

Intrinsic PEEP monitored in the ventilated ARDS patient with a mathematical method.

Under mechanical volume-controlled ventilation, the intensive care patient can develop intrinsic positive end-expiratory pressure (iPEEP); that is, the passive expiration is terminated by the following inspiration before the alveolar pressure comes to its physical equilibrium value. We present a mathematical method to estimate this alveolar dynamic iPEEP breath by breath, without the need of a maneuver. We tested it in paralyzed patients ventilated for adult respiratory distress syndrome after multiple trauma and/or sepsis, and we compared the results obtained with the new mathematical method with those from the occlusion method introduced by Pepe and Marini. The results agreed well (median difference of 0.8 mbar in 201 investigations in 12 patients). However, the mathematically determined values, representing dynamic iPEEP, are systematically slightly smaller than those measured by the occlusion maneuver. A variation of expiratory time suggests that this difference might be due to mechanical time-constant inhomogeneity, viscoelastic processes, or other mechanisms showing time dependence.     

The treatment of cluster headache with relaxation and thermal biofeedback

Eleven patients with episodic cluster headache were assessed and offered a treatment program consisting of 8 weeks of training in abbreviated progressive relaxation followed by 12 sessions of thermal biofeedback. Four dropped out before treatment began. Of the seven who completed the full treatment regimen, three (27% of initial sample) reported some degree of improvement when their next cluster bout occurred. In no one was the disorder eliminated.This research was supported by a grant from the National Institute of Neurological and Communicative Disorders and Stroke, NS-15235.     

ISOLATION AND PARTIAL CHARACTERIZATION OF NITRATE ASSIMILATION MUTANTS OF DUNALIELLA TERTIOLECTA (CHLOROPHYCEAE)1

Fifteen nitrate assimilation-deficient mutants of the euryhaline green alga, Dunaliella tertiolecta Butcher were selected by their chlorate resistance. Ten mutants, unable to grow on NO₃^? but able to grow on NO₂^?, had no detectable nitrate reductase activity. Five mutants, unable to grow on either NO₃^? or NO₂^?, had depressed levels of both nitrate and nitrite reductase. A method for assaying methyl viologen-nitrate reductase in the presence of nitrite reductase is described.     

Variance in the production of homovanillic acid and 3-methoxy-4-hydroxyphenethyleneglycol by the awake primate brain

Previous experimental results, using a new technique whereby the production rates of the neurotransmitter metabolites homovanillic acid (HVA) and 3-methoxy-4-hydroxyphenethyleneglycol (MHPG) by the awake primate brain are determined, have shown a wide variance in metabolite production among both animal and human subjects. These data suggested that either individual subjects differ in the activity of brain dopamine (DA) or norepinephrine (NE) neurons and/or that the activities of these neurons fluctuate over time. For these reasons a series of experiments were performed in which measures of HVA and MHPG production were obtained at three time points in the same animal (monkeys) over a three hour period. It was found that the group mean values for the production of HVA and MHPG by brain were similar for each of the three time points. However, it was also found that marked variations in HVA and MHPG production occur within a single animal over a three hour period. The coefficients of variation for individual animals for HVA ranged from 9.3 to 31.9% and for MHPG from 10.1 to 62.3%. These variations were not correlated with grossly observable changes in behavioral states. Using an analysis of variance it was found that the variance in MHPG production was significantly greater than that for HVA (F = 6.2, p < 0.05) suggesting that brain NE systems are more liable and/or show greater change than do brain DA systems. These data are interpreted as indicating that in the awake, resting primate brain fluctuations in the activities of DA and NE neurons occur, i.e. there is not a steady, invariant production of metabolites but rather they are produced in pulses of varying lengths. This interpretation of the data is generally consistent with electrophysiological studies which indicate that catecholamine neurons fire in bursts which are then followed by silent periods. Finally, in terms of practical application of the V-A difference technique, these data indicate that replicable group mean estimates of brain HVA and MHPG production can be obtained by averaging values from a single time point whereas accurate information about an individual animal will require multiple samplings.Recent reports from this laboratory have described a method whereby a direct measure of the rates of production of neurotransmitter metabolites such as homovanillic acid (HVA), 3-methoxy-4-hydroxyphenethyleneglycol (MHPG), and 5-hydroxyindoleacetic acid (5-HIAA) by the awake primate brain can be determined (1, 2, 3, 4). Since the quantities of HVA, MHPG, and probably 5-HIAA in the brain vary as a function of the activity of dopamine (DA), norepinephrine (NE), and serotonin (5-HT) neurons (1, 5, 6, 7, 8), it is likely that these measures of neurotransmitter metabolite production reflect the functional state of brain DA, NE, and 5-HT neuronal systems. The experimental results thus far obtained with this technique have shown a wide variance in the rates of neurotransmitter metabolite production across both animal and human subjects even though the subjects were not in clearly different behavioral or emotional states (1, 2, 4, 9). These data suggested that either individual subjects differ markedly in the activities of brain DA, NE, and 5-HT neurotransmitter systems and/or that the activity of these systems fluctuates markedly over time. For these reasons, experiments were undertaken in which repeated measures of HVA and MHPG production by brain within the same animal were determined over a three hour period. The results of these experiments, which are reported here, indicate that there are marked changes in brain metabolite production which occur within animals. The implications of these findings for our understanding of the functioning of brain neurotransmitter systems and for the practical applications of this technique are discussed.