Physicochemical and structural studies onAcinetobacter calcoaceticus RAG-1 and MR-481—Two standard strains in hydrophobicity tests

Acinetobacter calcoaceticus RAG-1 and MR-481, two standard strains used in microbial adhesion to hydrocarbons (MATH), were characterized by contact angles, pH-dependent zeta potentials, elemental surface composition by X-ray photoelectron spectroscopy (XPS), and molecular composition by infrared spectroscopy (IR). Negatively stained (methylamine tungstate) and ruthenium red-stained cells were studied by transmission electron microscopy to reveal the absence or presence of surface appendages. Despite the fact thatA. calcoaceticus RAG-1 is known to be extremely hydrophobic in MATH, whereas MR-481 is a completely non-hydrophobic mutant, neither XPS nor IR indicated a significant difference in chemical composition of the cell surfaces. Contact angles with polar liquids, water and formamide, were considerably higher on RAG-1 than on MR-481, in accordance with their relative hydrophobicities as measured by MATH. However, no significant differences in contact angles were observed between the two strains with apolar liquids like diiodomethane,-bromonaphthalene, and hexadecane. Fibrous extensions on RAG-1, observed after ruthenium red staining, were absent on the non-hydrophobic mutant MR-481. Tentatively, these extensions could be held responsible for the hydrophobicity ofA. calcoaceticus RAG-1.     

The involvement of ethanol in the free radical reaction of 6-hydroxydopamine

ESR spin trapping technique was used to detect and analyze free radical formation. When 6-hydroxydomine (6-OHDA) was incubated alone or in the presence of a free radical generating system (H₂O₂ and FeSO₄), hydroxyl free radicals were observed in a concentration-dependent manner. Glutathione was found to be the most effective scavenger of the ESR signal when compared with vitamin E or Mannitol. The addition of ethanol resulted in the formation of the pure hydroxyethyl free radicals. The amount of hydroxyethyl free radicals in the system was dependent upon the concentration of ethanol and the formation of hydroxyethyl free radicals correlated well with the extent of lipid peroxidation and the loss of enzymic activity of the membrane-bound (Na⁺, K⁺)-ATPase. We suggest that in the biological system ethanol may potentiate the neurotoxicity of 6-OHDA with the formation of hydroxyethyl free radicals, which are longer-lived and far more damaging to membranes that the hydroxyl radicals. These data lead us to further hypothesize that the neuronal degeneration caused by 6-OHDA and other compounds that generate free radicals could be potentiated in the presence of ethanol.     

Chromatid repulsion associated with Roberts/SC phocomelia syndrome is reduced in malignant cells and not expressed in interspecies somatic-cell hybrids.

Different cell types from a female patient with Roberts/SC phocomelia syndrome were evaluated quantitatively for the presence of repulsion of heterochromatin and satellite regions of mitotic chromosomes. Whereas EBV-transformed lymphoblasts from an established cell line revealed these phenomena at frequencies equal to those in PHA-stimulated lymphocytes and cultured skin fibroblasts, aneuploid cells from a metastatic melanoma displayed them at 50% lower frequency. Cocultivation of the patient's fibroblasts with either an immortal Chinese hamster cell line or with a human male fibroblast strain carrying a t(4;6)(p14;q21) translocation showed that the phenomenon was not corrected or induced by a diffusible factor or by cell-to-cell contact. In each experiment, only the patient's metaphase spreads revealed chromatid repulsion. In fusion hybrids between the patient's fibroblasts and an established Chinese hamster cell line, the human chromosomes behaved perfectly normally, suggesting that the gene product which is missing or mutant in Roberts/SC phocomelia syndrome is supplied by the Chinese hamster genome.     

Tubulin pseudogenes as markers for hominoid divergence

Processed pseudogenes arise via unimolecular events that result in the integration of nonfunctional (and therefore non-selected) regions of DNA into the germ line. The sequence of such pseudogenes can be used as a novel form of evolutionary clock: the older a particular pseudogene, the more mutations it has acquired relative to the selectively constrained functional gene from which it was originally derived. We have used specific beta-tubulin gene probes to assay for the presence of fully sequenced processed pseudogenes in genomic DNA from various hominoid species. The data suggest that orangutan is more closely related to human, chimpanzee and gorilla than is generally believed.     

Crystallization and preliminary crystallographic data of the Fab fragment of an anti-phenylalanine hydroxylase monoclonal antibody

Two crystal habits, one rod shaped and the other square prismatic, of the Fab fragment of a monoclonal anti-phenylalanine hydroxylase antibody have been grown using the method of vapour phase diffusion against polyethylene glycol 6000. The square prisms diffract to better than 2.8 A, belong to the space group P1 and have unit cell parameters a = 41.8 A, b = 50.3 A, c = 114.7 A, alpha = 97.6 degrees, beta = 91.7 degrees, gamma = 91.0 degrees, while the rod-shaped crystals belong to the space group P212121, have unit cell parameters a = 105.6 A, b = 119.8 A, c = 82.2 A and diffract to 3.5 A resolution.     

Secretory bursts of growth hormone secretion in the dog may be initiated by somatostatin withdrawal

In 28 6-h experiments on 10 conscious resting trained male dogs, plasma growth hormone (GH) was determined at 5-min intervals by radioimmunoassay. For all experiments, the basal GH concentration in plasma was 0.80 +/- 0.06 ng mL-1. In each experiment, 1-3 secretory bursts of GH occurred, raising plasma GH 2.4 to 15.3 times basal concentrations (for all 43 bursts, 6.6 +/- 0.4 times the basal value). Metabolic clearance rates (MCR) and apparent distribution volumes (V) were determined, using stepwise infusions of canine GH. The MCR (3.99 +/- 0.30 mL kg-1 min-1) and V (57.9 +/- 5.5 mL kg-1) were used to transform the GH concentration versus time data into GH secretion rates, using a single compartment approach. Basal GH secretion rates for all 28 experiments were 3.12 +/- 0.24 ng kg-1 min-1. The secretory bursts yield peak GH secretion rates of 9.4 +/- 0.8 times basal secretion and these steep-sloped bursts last 25.1 +/- 1.2 min. Six-hour infusions of 0.15 microgram kg-1 min-1 of somatostatin (SRIF) abolished all secretory bursts but did not lower basal secretion rates. In five of seven SRIF infusion experiments in which samples were taken after the infusion ceased a secretory burst was seen in the hour following cessation of infusion (in four cases within 10 min). These secretory bursts lasted 23.0 +/- 2.9 min and were similar to those seen in control experiments. Infusions of SRIF at 0.05 microgram kg-1 min-1 had no effect. These results imply that during basal GH secretion, a surfeit of SRIF impinges on the somatotrophs, as extra SRIF does not further lower basal secretion. However, during secretory bursts, very little SRIF must be present, as exogenous SRIF blocks these bursts. The bursts are similar in duration to overshoots provoked in perifused dispersed rat somatotrophs by removal of an SRIF signal. It seems likely that their cause in vivo is similar. (All values are means +/- SEM.)     

Feedback suppression of ACTH secretion by cortisol in dogs: lags after large signals equal those following very small signals

Previously, low stepwise infusions of cortisol in resting adrenalectomized dogs (plateaux less than or equal to 6 micrograms/dL) were shown to reduce ACTH secretion only after 20 min. In the present study, large, steep-sloped cortisol signals were used to try to evoke faster feedback. Adrenalectomized male mongrel dogs were maintained on exogenous steroids until 48 h before the experiment. Of the 23 experiments on 15 dogs (under light pentobarbital anesthesia), 12 were on resting dogs, 7 on dogs stressed by variable insulin infusion (keeping plasma glucose at 18-40 mg/dL), and 4 stressed as above but with 4 h of low cortisol infusion (plasma congruent to 5 micrograms/dL) before applying the feedback signal. After a 50-min control period, a 30-min feedback period was initiated by one of two i.v. cortisol signals: (a) injection of 0.3 mg/kg or (b) infusion of 46 micrograms kg-1 min-1. Both raised plasma cortisol above physiological limits (within 2 and 6 min, respectively). In each experiment, 23 timed venous blood samples were assayed for plasma ACTH and cortisol. ACTH secretion rates were calculated continuously using a validated single-compartment method. Results from both types of cortisol signals were indistinguishable, and were thus pooled. In the unstressed dogs, control-period ACTH secretion of 0.97 +/- 0.12 mU kg-1 min-1 showed no significant decline due to the feedback signal for 20.3 +/- 1.4 min.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of pinealectomy on seasonal changes in antler growth and concentrations of testosterone and prolactin in white-tailed deer

A 2-year study was conducted to determine under controlled conditions the role of the pineal gland in regulating the seasonal changes in antler growth and reproduction of male white-tailed deer. Blood samples were drawn from 6 pinealectomized (PX) and 18 control (C) deer at intervals of 2 weeks and analyzed for testosterone (T) and prolactin (Prl). Relative scrotal circumference and main beam antler length were recorded. Relative scrotal circumference was similar in PX and C groups, but the normal pattern was delayed 1 to 3 months in the PX deer relative to the C deer. The mean dates of beginning antler growth, velvet shedding, antler casting and pelage changes were significantly later in both years for PX deer than in C deer. Testosterone concentrations peaked 1 month later in the PX deer than in the C deer for both yearling and 2-year-old deer. Prl concentrations in C deer, but not in PX deer, were correlated highly with day length, and the PX deer were delayed relative to the C deer in showing the normal Prl pattern. Increasing levels of Prl in both groups coincided with beginning antler growth in both years. These results indicate that the pineal gland does not originate the seasonal cycles of male white-tailed deer but may synchronize cycles among individual deer, and regulate the circannual rhythm of Prl concentrations which may in turn influence other hormonal cycles.     

The relative role of stomata in transpiration and assimilation

Summary The ways in which transpiration and assimilation depend on stomatal aperture are compared. It is shown that transpiration and assimilation are equally sensitive to change of stomatal aperture when the internal resistance to assimilation is equal to an effective resistance to evaporation which exists because of the coupling of heat and vapour exchanges between leaf and atmosphere. Generally the ratio of transpiration to assimilation changes with stomatal aperture in a manner which is determined by the relative magnitude of these resistances and on temperature. Some possible implications in relation to the optimal behaviour of stomata are discussed.Work done while J.H.T. held a New Zealand D.S.I.R. Fellowship.     

The Influence of Morphology on Prognosis in Acute Leukemia

The presence of definite cytoplasmic granulation in at least some of the malignant cells was used as the sole criterion to separate 156 patients with acute leukemia into two groups: 110 with myeloblastic (AML), and 46 with lymphoblastic or stem cell leukemia (ALL). The median survival from the onset of symptoms in patients with AML was 20 weeks, and those with ALL 37 weeks. The difference in survival in these two groups is much greater for patients under the age of 25 than for those over the age of 25.