Desipramine Binding: Relationship to Central and Sympathetic Noradrenergic Activity

We examined the effects of treatments affecting norepinephrine release on the number of norepinephrine reuptake recognition sites as reflected by desipramine binding. To do this, we used manipulations having similar presynaptic but contrasting postsynaptic effects. Presynaptic inhibition by 6-hydroxydopamine lesion or by clonidine, and postsynaptic receptor stimulation by isoproterenol, reduced desipramine binding. Presynaptic stimulation by d-amphetamine and postsynaptic receptor blockade by prazosin increased desipramine binding. Similar effects and binding properties were seen in cerebral cortex, heart, and soleus muscle. After unilateral noradrenergic lesions, reduction in desipramine binding correlated with reduction in norepinephrine uptake. These results show that norepinephrine reuptake appears to be regulated by transmitter release regardless of effects on postsynaptic transmission, and that this regulation is analogous in the central and sympathetic nervous systems.     

Quinolinic Acid Phosphoribosyltransferase in Rat Brain

Because of the possible participation of quinolinic acid in brain function and/or dysfunction, the characteristics of its catabolic enzyme, quinolinic acid phosphoribosyltransferase (QPRTase; EC 2.4.2.19), were examined in rat brain tissue. For this purpose, a sensitive radiochemical assay method, based on the conversion of quinolinic acid to nicotinic acid mononucleotide (NAMN), was developed. For brain QPRTase, the Mg2+ dependency, substrate specificity, and optimal assay conditions were virtually identical to those of the liver enzyme. Kinetic analyses of brain QPRTase revealed a Km of 3.17 +/- 0.30 microM for quinolinic acid and Km = 65.13 +/- 13.74 microM for the cosubstrate phosphoribosylpyrophosphate. The respective Vmax values were: 0.91 +/- 0.08 pmol NAMN/h/mg tissue for quinolinic acid and 11.65 +/- 1.55 fmol NAMN/h/mg tissue for phosphoribosylpyrophosphate. All kinetic parameters measured for the brain enzyme were significantly different from those determined for liver QPRTase, indicating structural differences or distinct regulatory processes for the brain and liver enzymes. Phthalic acid was a potent competitive inhibitor of brain QPRTase. Examination of the regional distribution of QPRTase in the rat CNS and retina indicated a greater than 20-fold difference between the area displaying the highest activity (olfactory bulb) and those of only moderate activity (frontal cortex, striatum, retina, hippo-campus). Enzyme activity was present at the earliest age tested, 2 days, and tended to increase in older animals. Brain QPRTase activity was preferentially located in the nerve-ending (synaptosomal) fraction. Enzyme activity was stable over extensive periods of storage at -80 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)     

A glycophospholipid covalently attached to the C-terminus of the Thy-1 glycoprotein

The Thy-1 glycoprotein is a very abundant cell surface molecule of rat thymocytes and neuronal cells with the properties of a molecule that inserts into the lipid bilayer. The hydrophobicity is due to a glycophospholipid component covalently attached to the carboxy group of the C-terminal cysteine residue. The mature glycoprotein does not contain a stretch of hydrophobic amino acids that could traverse the membrane bilayer. These findings present a new mode of membrane attachment for a cell surface molecule that can mediate lymphokine release and cell division after cross-linking by antibodies.     

Allometries of the durations of torpid and euthermic intervals during mammalian hibernation: A test of the theory of metabolic control of the timing of changes in body temperature

Summary The durations of the intervals of torpor and euthermia during mammalian hibernation were found to be dependent on body mass. These relationships support the concept that the timing of body temperature changes is controlled by some metabolic process. Data were obtained from species spanning nearly three orders of magnitude in size, that were able to hibernate for over six months without food at 5°C. The timing of body temperature changes was determined from the records of copper-constantan thermocouples placed directly underneath each animal. Because all species underwent seasonal changes in their patterns of hibernation, animals were compared in midwinter when the duration of euthermic intervals was short and relatively constant and when the duration of torpid intervals was at its longest. Large hibernators remained euthermic longer than small hibernators (Fig. 2). This was true among and within species. The duration of euthermic intervals increased with mass at the same rate (mass^0.38) that mass-specific rates of euthermic metabolism decrease, suggesting that hibernators remain at high body temperatures until a fixed amount of metabolism has been completed. These data are consistent with the theory that each interval of euthermia is necessary to restore some metabolic imbalance that developed during the previous bout of torpor. In addition, small species remained torpid for longer intervals, than large species (Fig. 3). The absolute differences between different-sized species were large, but, on a proportional basis, they were comparatively slight. Mass-specific rates of metabolism during torpor also appear to be much less dependent on body mass than those during euthermia, but the precision of these metabolic measurements is insufficient for them to provide a conclusive test of the metabolic theory. Finally, small species with high mass-specific rates of euthermic metabolism are under tighter energetic constraints during dormancy than large species. The data presented here show that, in midwinter, small species compensate both by spending less time at high body temperatures following each arousal episode and by arousing less frequently, although the former is far more important energetically than the latter.     

Mapping X-linked ophthalmic diseases: II. Linkage relationship of X-linked retinitis pigmentosa to X chromosomal short arm markers

Summary X-linked retinitis pigmentosa (XLRP) is a series of hereditary dystrophic diseases of the retina that occur in three clinically distinguishable variants: the classic form (McK-31360), a type known as choroidoretinal dystrophy (McK-30330), and a variant with golden-metallic or tapetal reflex in the heterozygote (McK30320). Controversy exists as to whether these phenotypic differences are due to clinical variability in disease expression, heterogeneity in disease alleles at a single locus, or a multiplicity of loci for XLRP. We have studied a single large kindred segregating for XLRP with the metallic fundus reflex in the heterozygote with restriction fragment length polymorphisms (RFLPs) from the short arm of the human X chromosome, and found measurable linkage to DXS7 (=12.5 cMorgans at LOD=2.5), the same RFLP previously shown by others to be tightly linked to the other forms of XLRP at =3cM. Although these estimates appeared to be different, each fell just within the 95% probability interval of the other and, therefore, were insufficient to prove or disprove that the metallic sheen form of XLRP is allelic with other forms of XLRP. Additional RFLPs at the DXS43 and the ornithine transcarbamoylase loci provided three-point crosses for determining the relative positions of DXS7 and XLRP, and supported an order that placed this form of XLRP distal to DXS7 on the Xp. Until the question of genetic heterogeneity is resolved, careful phenotypic characterization of the clinical type of XLRP present in families being used for linkage analyses is advisable.Presented in part at the American Society of Human Genetics meeting, Toronto, Canada, November 1, 1984     

Maturation of pig and rat oocytes transplanted into surrogate pig follicles in vitro

Pig oocytes obtained from slaughterhouse material and rat oocytes obtained from PMSG-treated immature females were incubated as isolated oocytes or injected into explanted pig follicles (5–8 mm). Free oocytes of both species, with or without their cumulus investment or gonadotropins during culture, matured at high rates after 30 hr or 9–10 hr of culture, respectively. Gonadotropic stimulation was necessary for maturation of both the native and injected cumulus-intact pig oocytes in follicle culture. Cumulus-free pig oocytes injected into follicle failed to mature in response to gonadotropic stimulation, suggesting an inability to perceive or respond to stimulation. Injected rat oocytes, however, matured irrespective of cumulus investment or gonadotropic stimulation. Their maturation was delayed and reduced at 9 hr. These results in the rat suggest that the pig follicular environment is incapable of regulating rat oocyte maturation but rather presents a permissive or supportive environment for their maturation. The explanted surrogate follicles from the pig or other species may provide a useful model for the study of oocyte-follicle interactions in oocyte maturation within or between species.     

The invasion of Biomphalaria pfeifferi by Schistosoma mansoni miracidia and the development of daughter sporocysts

Laboratory experiments have been carried out to determine the susceptibility of Gezira Biomphalaria pfeifferi snails to S. mansoni miracidia and the relationship between miracidia and daughter sporocyst production at the 10–17 day development stage. The relationship between snail numbers, miracidia numbers and water volume has also been studied. Two non susceptible snails, Bulinus truncatus and Cleopatra bulimoides, both of which occur naturally in Gezira canals, were tested to see if they act as decoys for S. mansoni miracidia.The results showed that the B. pfeifferi are 100% susceptible to S. mansoni invasion, at least to the daughter sporocyst development stage. The more miracidia that penetrated the more daughter sporocysts were produced, however individual variation and overlap were great. When one miracidium was released to find one snail it succeeded in low water volumes (5 m, 50 ml), but failed in 5 litres. When 100 miracidia were released mortality of snails was high suggesting superinfection particularly when only one or five snails were available. Among survivors daughter sporocyst counts were very high. Cleopatra and Bulinus snails do have a decoy effect when present in large numbers. In their presence the number of infected snails was marginally reduced and the number of daughter sporocysts greatly reduced. However, if superinfection is reduced by decoy effect, it is conceivable that Biomphalaria may be protected by decoy snails in circumstances where miracidia counts are high.     

Identification of a tumor inhibitory factor in rat ascites fluid

A polypeptide which inhibits the growth of human carcinoma cells has been characterized from Novikoff rat ascites fluid. This tumor inhibitory factor co-purified with transforming growth factor activity through acid/ethanol extraction and Bio-Gel chromatography. The two activities were completely separated by reverse phase HPLC. The tumor inhibitory factor is heat stable and requires disulfide bonds for bioactivity. This factor inhibited the anchorage independent growth of the more differentiated human colon carcinoma cell lines but did not affect the less differentiated carcinoma cells. The presence of stimulatory and inhibitory activities in the same extracts suggests that the relative concentrations of these factors may be important in the control of cell growth.     

Effects of ultraviolet-B radiation on plants during mild water stress. IV. The insensitivity of soybean internal water relations to ultraviolet-B radiation

The combined effects of ultraviolet-B (UV-B, 280–320 nm) radiation and water stress were investigated on the water relations of greenhouse grown soybean [ Glycine max (L.) Merr. cv. Essex]. On a weighted (Caldwell 1971), total daily dose basis, plants received either 0 or 3 000 effective J m² UV-B_BE supplied by filtered FS-40 sunlamps. The latter dose simulated the solar UV-B radiation anticipated at College Park, Maryland, U.S.A. (39°N latitude) in the event that the global stratospheric ozone column is reduced by 25%. Plants were either well-watered or preconditioned by drought stress cycles. Diurnal measurements of water potential and stomatal conductance were made on the youngest fully expanded leaf. Various internal water relations parameters were determined for detached leaves. Plants were monitored before, during and after water stress. There were no significant differences in leaf water potential or stomatal conductance between treatments before plants were preconditioned to water stress. However, drought stress resulted in significantly lower midday and afternoon leaf water potentials and lower leaf conductances as compared to well-watered plants. UV-B radiation had no additional effect on leaf water potential; however, UV did result in lower leaf conductances in plants preconditioned to water stress. Turgid weight:dry weight ratio, elastic modulus, bound water and relative water content were unaffected by UV-B radiation. Osmotic potentials at full and zero turgor were significantly lower in the drought stressed treatments as compared to well-watered plants.     

Effects of ultraviolet-B radiation on plants during mild water stress. III. Effects on photosynthetic recovery and growth in soybean

Soybean { Glycine max (L.) Merr. ev. Essex} was grown from seed in a greenhouse under ultraviolet-B (UV-B, 280–320 nm) radiation supplied by filtered FS-40 sunlamps. On a weighted, total daily dose basis these plants received either 0 (control) or 2875 effective J m⁻² day⁻¹ UV-B_BE. When weighted with the generalized plant action spectrum (Caldwell 1971), this simulated the solar ultraviolet-B irradiance expected to occur at College Park, Maryland, USA (39°N) in the event the global stratospheric ozone column is reduced by 23%. The effects of ultraviolet radiation on the photosynthetic recovery from water stress were measured with an infrared gas analyzer. These effects were examined in plants which were either well-watered or previously preconditioned to water stress, during two distinct phenological stages of development. During the early stages of soybean growth, enhanced levels of UV-B reduced net photosynthesis by 25%, and water stress also reduced photosynthesis to nearly the same extent (by 20%). The combination of these two stresses resulted in smaller biomass than that produced by plants exposed to either stress independently. Photosynthesis in older, larger plants was much more sensitive to water stress and was reduced by as much as 50–60% in non-preconditioned plants. Although non-irradiated, non-preconditioned (control) plants recovered to only within 60% of their prestressed value, preconditioned plants recovered to within 70–80% during the 3 day recovery period. Both water stress and UV-B radiation affected non-stomatal conductance, while stomatal conductance was primarily affected by water stress.