Effect of ascorbic acid on heme metabolism in hepatic microsomes

Hepatic microsonal cytochrome P-450 levels are significantly decreased (46–68%) in ascorbic acid-deficient guinea pigs. Studies attempting to elucidate the mechanism responsible for decreased cytochrome P-450 demonstrated that ascorbic acid status did not influence the turnover $\text{(}\text{t}\text{1}\text{2}\text{)}$ or the degradation of hepatic cytochrome P-450 heme. Urinary excretion of Δ-aminolevulinic acid (ALA) and coproporphyrin was significantly decreased (30 and 69% respectively) in ascorbic acid-deficient guinea pigs. Injections (ip) of ALA into ascorbic acid-deficient guinea pigs were not effective in returning cytochrome P-450 levels to values found in ascorbic acid-supplemented guinea pigs. In addition, plasma and hepatic iron and blood heme were related directly, while hepatic copper and plasma copper or ceruloplasmin were related inversely, to the ascorbic-acid status of the guinea pig. These data, along with past investigations on heme synthesis in the ascorbic acid-deficient guinea pig, are consistent with mechanisms proposing that ascorbic acid may influence: 1) apocytochrome P-450 synthesis, 2) binding of heme and apo-cytochrome P-450 to form active cytochrome P-450, and/or 3) incorporation of Fe++ into the heme moiety of cytochrome P-450, perhaps via changes in copper metabolism.     

Effect of prostaglandin E2 on vascular responses of the rabbit kidney to nerve stimulation and noradrenaline, in vitro and in situ

The effect of prostaglandin E₂ on vascular responses of the rabbit kidney to renal nerve stimulation and noradrenaline was examined $\text{in}$$\text{vitro}$ and $\text{in}$$\text{situ}$ as a test of the hypthesis that prostaglandins of the E series may be involved in the regulation of adrenergic neuroeffector transmission. Intraarterial administration of prostaglandin E₂ to the $\text{in}$$\text{vitro}$ kidney caused marked inhibition of vascular responses to nerve stimulation whereas the responses to noradrenaline were not significantly altered. In the $\text{in}$$\text{situ}$ preparation, vascular responses to both nerve stimulation and noradrenaline were inhibited by prostaglandin E₂ infusion, although its effect on responses to nerve stimulation was approximately twice that observed on responses to noradrenaline.It is concluded that prostaglandin E₂ acts primarily at a prejunctional level of adrenergic neuroeffector transmission in the kidney, although a postjunctional effect has also been observed.     

Cellular compartmentation of two species of δ-aminolevulinic acid synthetase in a facultative photohetero-trophic bacterium (Rps. spheroides Y.)

Both species of δ-aminolevulinic acid (ALA) synthetase appear compartmentalized in $\text{Rps. spheroides}$ Y. The ALA synthetase, “F_I”, activity is correlated with dark respiratory metabolism and is a cytoplasmic “soluble” enzyme. The other enzyme, “F_II”, induced only in light, is in chromatophores and its activity is correlated with photometabolism.     

Induction of tyrosine hydroxlase synthesis in rat superior cervical ganglia in vitro by nerve growth factor and dexamethasone.

The addition of dexamethasone and nerve growth factor to organ cultures of superior cervical ganglia from young rats induces the synthesis of tyrosine hydroxylase. The combination of nerve growth factor and dexamethasone $\text{in vitro}$ produces a differential rate of tyrosine hydroxylase synthesis which approaches that obtained by the $\text{in vivo}$ administration of nerve growth factor.     

Glycine metabolism and chlorophyll synthesis in barley leaves

α-Hydroxypyridine methane sulphonic acid (HPMS), isonicotinyl hydrazide (INH) and nialamide inhibit chlorophyll synthesis in etiolated barley leaves exposed to light. HPMS lowered the rate of protochlorophyllide regeneration but had little effect on the synthesis of protochlorophyll (P630) from exogenous $\text{δ}$-aminolaevulinic acid (ALA). The addition of glycine to HPMS treated leaves partially overcame the inhibition of chlorophyll synthesis. Glycine-[¹⁴C] was readily incorporated into ALA in dark-grown leaves. HPMS treatment increased the sp. act. of ALA in leaves fed glycine-[¹⁴C]. Glycollate oxidation was lower in extracts from HPMS treated leaves. Plants may therefore have two pathways for ALA production with the glutamate pathway becoming more important in conditions where photorespiration is high.     

Attenuation of noradrenergic neurotransmission by the thromboxane synthetase inhibitor,UK 38,485

The purpose of this study was to determine the effects of chronic administration of the thromboxane synthetase inhibitor, UK 38,485, on noradrenergic neurotransmission. Male Sprague Dawley rats (n=14) were treated once daily with either UK 38,485 (100 mg/kg; n=7) or the vehicle of UK 38,485 (olive oil; n=7) by gavage. The dose of UK 38,485 chosen was sufficient to inhibit $\text{ex vivo}$ platelet TXB₂ production by >90% for 24 hours. One week into the treatment animals were prepared for $\text{in situ}$ perfusion of their mesenteric vascular beds. Vasoconstrictor responses to both exogenous norepinephrine and periarterial nerve stimulation were determined both before and during an infusion of angiotensin II (9ng/min) into the superior mesenteric artery. UK 38,485 significantly (P<0.02) attenuated the vascular response to periarterial nerve stimulation without altering the vascular response to either norepinephrine or angiotensin II. UK 38,485 did not influence the baseline perfusion pressure, the mean arterial blood pressure or the potentiation of neurotransmission by angiotensin II. These data indicate that in the $\text{in situ}$ rat mesentery UK 38,485 attenuates the release of neurotransmitter from sympathetic nerve terminals.     

Inhibition of δ-aminolevulinic acid synthetase and δ-aminolevulinic acid dehydrase by L-2-amino-4-methoxy-trans-3-butenoic acid in the rat

The rate limiting enzyme of heme biosynthesis, δ-aminolevulinic acid synthetase (ALA synthetase), and the second enzyme in the heme biosynthetic pathway, δ-aminolevulinic acid dehydrase (ALA dehydrase), were inhibited by the olefinic amino acid L-2-amino-4-methoxy - $\text{trans}$-3-butenoic acid (AMTB). Administration of AMTB (20 mg/kg; i.p.) to rats inhibited ALA synthetase and ALA dehydrase in control animals and in animals with markedly elevated activity of ALA synthetase which resulted from the administration of 3,5-dicarbethoxy-1,4-dimethyl-collidine (DDC, 200 mg/kg, i.p.) or allylisopropylacetamide (200 mg/kg, s.c.). AMTB also blocked the synthesis of rat hepatic porphyrins and inhibited the increase in the urinary excretion of δ-aminolevulinic acid and porphobilinogen following DDC (150 mg/kg, p.o.) administration. Preincubation of AMTB with liver mitochondria or a soluble fraction of liver decreased the activity of mitochondrial ALA synthetase and soluble ALA dehydrase, respectively.     

The dimer-monomer equilibrium constant for [125I]β nerve growth factor

The equilibrium constant for $\text{[}{}^{125}\text{I]β}$ nerve growth factor was determined using polyacrylamide gel electrophoresis to separate the monomer and dimer. Various concentrations of the radiolabelled nerve growth factor were incubated for 24 and 48 hours. The equilibrium constants obtained for both incubation periods were the same, 3.2 ± 1.4 × 10^?11$\text{M}$ and 2.6 ± 1.6 × 10^?11$\text{M}$, respectively. Thus, at physiological concentrations the β nerve growth factor is in the dimeric form almost exculsively.     

A dynamic X-ray diffraction study of anesthesia action. Thickening of the myelin membrane by n-pentane

The structural changes induced in the myelin sheath by $\text{n-}\text{pentane}$ nerve impulse blockage were studied by small-angle X-ray diffraction using a linear position-sensitive detector. The results show that the thickness of the myelin period lattice increases from 170 to 180 Å during $\text{n-}\text{pentane}$ treatment.     

Effect of heat on frog sciatic nerve determined by X-ray diffraction

Low-angle X-ray diffraction patterns have been recorded from frog sciatic nerves in Ringer's solution after heat treatment from 20 to 80°C. The X-ray patterns were obtained from the heat treated specimens after cooling to room temperature. The normal X-ray pattern of frog sciatic nerve in Ringer's solution with $\text{d=171}\text{A}\text{?}$ was maintained from 20 to 58°C. Above 58°C, a new high temperature pattern based on a repeat period of $\text{d?435}\text{A}\text{?}$ was recorded from the nerve in Ringer's solution. The physical state of nerve myelin after heat teratment at a temperature ?58°C has been identified as the anomalous swollen state. Anomalous swelling takes place in units of four membranes.     

The metabolic fate of [porphyrin-14C] cytochrome c in dogs.

[Porphyrin-¹⁴C] cytochrome $\text{c}$ (isolated from tissues of dogs injected with [¹⁴C] ALA) was given intravenously to one normal and one bile fistula dog. Essentially all of the injected ¹⁴C was excreted in the urine during the first six days. No (unchanged) cytochrome $\text{c}$ was detectable in the urine. Analysis of ¹⁴C and of light absorption at 400 nm in the successive eluates from Florisil columns showed that all ¹⁴C peaks coincided with pigment peaks, but some pigment peaks has no increase in ¹⁴C. The relative distribution of ¹⁴C in these pigment peaks changed markedly between the first and third days. Delayed excretion of some ¹⁴C suggested cellular uptake of cytochrome $\text{c}$ prior to the urinary excretion of its endogenous metabolites.     

Effect in vivo of a sub-hypnotic dose of ethanol on nerve conduction velocity in mice

Relative nerve conduction time (reciprocal of velocity), before and after administration of ethanol, was studied in the caudal nerves of 58 mice. Doses of 1.4, 2.0, 2.5, 3.0, and 4.24 g ethanol/kg body wt., given i.p., were used. The tail was maintained at 37.0° and a control (saline) injection preceeded the ethanol injection. Doses of 1.4 and 2.0 g/kg did not produce significant effects on conduction time but doses of 2.5, 3.0, and 4.24 g/kg did, the relative conduction times twelve minutes after ethanol increasing by 1.2, 1.8, and 3.1 percent, respectively. This appears to be the first controlled demonstration of an acute $\text{in}$$\text{vivo}$ effect of ethanol on conduction velocity.     

Electrophoretic measurements about the relation between transition voltage and ζ-potential of biological membranes

The effects of inorganic cations, $\text{n-}\text{hexanol}$, saccharose and ²H₂O on the electrophoretic mobility and ζ-potential of membrane vesicles from nerve myelin were measured and the results compared with the corresponding effects of the same reagents on the transition voltage, $\text{V}{}_{\mathrm{<mtext>Tr</mtext>}}$, of the nerve axon membrane. Different cation concentrations and ²H₂O affect both potentials, the ζ-potential and $\text{V}{}_{\mathrm{<mtext>Tr</mtext>}}$, in a parallel way. Saccharose and $\text{n-}\text{hexanol}$, however, shift $\text{V}{}_{\mathrm{<mtext>Tr</mtext>}}$ but leave the electrophoretic mobility of the myelin vesicles unchanged. These results suggest that $\text{V}{}_{\mathrm{<mtext>Tr</mtext>}}$ shifts are not necessarily linked to changes in the membrane surface charge density but may also be caused by an interaction between the reagent and non-polar groups of the membrane interior.     

X-ray diffraction analysis of dehydrated myelin

Improved X-ray diffraction data from dry nerve myelin are presented. In addition to the spacings of approx. 150 Å, 60 Å, 44 Å and 34.6 Å, which have been previously reported, we identify a 14 Å series. The data suggests that the hydrocarbon chains in the single bilayer ($\text{≈ 60}\text{A}\text{?}$) is ordered, whereas in the double bilayer ($\text{≈ 150}\text{A}\text{?}$) and in the fluid phase ($\text{≈ 44}\text{A}\text{?}$) it is disordered. It is shown that cholesterol ($\text{≈34.6}\text{A}\text{?}$) exists as a bilayer, and the 14 Å series is probably another cholesterol phase.     

In vitro synthesis of nerve growth factor related glioma C6 cell polypeptides.

Rat glioma C₆ cell polyribosomal preparations were tested in a heterologous $\text{in vitro}$ system for their ability to direct the synthesis of nerve growth factor related polypeptides. Two major polypeptides of MW ～ 21,000 and ～ 43,000 respectively were found, both of which were immunoprecipitable with specific anti-mouse 2.5S nerve growth factor serum. After incubation of $\text{in vitro}$ synthesized proteins with submaxillary gland extract the bulk of these protein species was converted into immunoprecipitable material of MW ～ 13,000, which comigrated in sodium dodecyl sulfate/polyacrylamide gel electrophoresis with mouse 2.5S nerve growth factor.     

Stimulus-coupled 3H-serotonin release from identified neurosecretory fibers in the spiny lobster, panulirusinterruptus

The stimulus-induced release of ³H-serotonin from pericardial nerve plexuses of the spiny lobster was studied $\text{in}$$\text{vitro}$. When incubated in radiolabeled tryptophan, these tissues synthesize and store considerable quantities of ³H-serotonin. ³H-serotonin is selectively released upon stimulation of the motor-ligamental nerve. The release is calcium-dependent and stimulus-coupled to a group of identified nerve processes exhibiting conduction velocities in the range of 0.8?1.0 m/sec. Stimulation of a single plexus at 30 Hz for 15 sec induces the release of 10 or more picomoles of ³H-serotonin, supporting the notion that serotonin serves a hormonal role in the Crustacea.     

Trypanosoma vivax: Courses of infection with three stabilates in inbred mouse strains

The courses of infection in inbred mouse strains were compared following infection with three Stabilates of high, intermediate, and low virulence of Trypanosoma vivax stock Zaria Y486. Mouse strains could only be shown to differ in their resistance to T. vivax infections as judged by the height of the initial parasitemia and survival times when a trypanosome population of low or intermediate virulence was used. A T. vivax population of high virulence was uniformly lethal. Comparison of lytic antibody titers between groups of resistant ($\text{C}\text{57}\text{B}\text{1}\text{6}$) and susceptible ($\text{Balb}\text{c}$) mice did not show any significant differences in titers of the surviving mice but the mice in either group which did not control the initial parasitemia had lower lytic antibody titers than those which did. A significantly larger number of $\text{Balb}\text{c}$ mice failed to control the initial infection as compared to the $\text{C}\text{57}\text{B}\text{1}\text{6}$. Treatment with cyclophosphamide did not ablate differences in susceptibility between the two strains. The use of congenic mice showed that these differences in susceptibility were not related to differences in the major histocompatibility complex between these strains.     

Effect of morphine sulfate on adenylate cyclase and phosphodiesterase activities in rat corpus striatum.

The effect of morphine sulfate (MS) on adenylate cyclase (AC) and phosphodiesterase (PDE) activities in the rat striatum was investigated. MS produced a dose-dependent increase in basal AC activity and did not alter sodium fluoride-induced stimulation both $\text{in}$$\text{vivo}$ (7.5–30 mg/kg, 1 hr pretreatment, i.p.) and $\text{in}$$\text{vitro}$ (1–100μM). $\text{in}$$\text{vitro}$, when submaximal effective concentrations of dopamine and MS were combined, there was an additive effect. However, administration of MS $\text{in}$$\text{vivo}$ did not alter dopamine-induced stimulation of AC activity. MS, $\text{in}$$\text{vitro}$ and $\text{in}$$\text{vivo}$ inhibited PDE activity in a dose-dependent manner only with the high substrate concentration (3.3 × 10⁻³M cyclic AMP). Preliminary results from this study indicate that morphine affects the cyclic AMP system.     

Funnel web spider venom produces spontaneous action potentials in nerve

Venom from the lethal Australian spider, $\text{Atrax robustus}$, causes fasciculation of muscles $\text{in vivo}$ and in isolated diaphragms in mice. Spontaneous end-plate potentials were recorded in muscle fibres exposed to the venom and associated spontaneous electrical activity could also be recorded from the phrenic nerve. It was proposed that the venom produces muscle fasciculation by causing abnormal, spontaneous, repetitive firing of motor nerves. The mechanism of this action was investigated in aplysia neurones. The venom produced abnormal, spontaneous, repetitive inward currents in voltage clamped neurones and changed the current-voltage characteristics of the surface membrane. It is suggested that the basic mode of action of Funnel-web venom is to change the electrical field in nerve membrane.     

Ribosome specificity for the formation of guanosine polyphosphates

Ribosomes obtained from $\text{Bacillus brevis}$ (ATCC 8185) were slightly active in synthesizing guanosine polyphosphates, which activity was greatly stimulated by addition of $\text{Escherichia coli}$ stringent factor. $\text{Chlamydomonas reinhardtii}$ chloroplast ribosomes did not produce guanosine polyphosphates on incubation but responded with abundant synthesis to addition of the stringent factor from $\text{E. coli}$. In contrast, cytoplasmic ribosomes from the same organism did not respond. Interchange experiments between either subunit from chloroplasts with the $\text{E. coli}$ counterparts showed good activity. When the small subunit of cytoplasmic $\text{Chlamydomonas}$ ribosomes was combined with the large subunit of $\text{E. coli}$ or of chloroplasts, a small but definite response was obtained.