Recent epidemiologic studies on nutrition and cataract in India, Italy and the United States

Three independent case-control studies with similar methodologies were conducted in India, the United States and Italy to investigate risk factors by cataract type. Their common objectives were to evaluate risk factors for each cataract type, giving priority to nutritional factors, and to determine whether risk factors differed among cataract types. Data included self-reporting of food frequencies and various biochemical determinations. A higher body mass index was the only nutritional factor found by more than one study to be associated with cataract, being less frequent in cases than in controls. Blood nutritional status from one study showed that a high antioxidant index decreased risk for at least one cataract type, high glucose-6-phosphate dehydrogenase values increased risk for at least one cataract type, a high albumin globulin ratio decreased risk for mixed cataract, and high iron levels decreased risk for cortical cataract. Only one of the three studies found that a high nutritional status, high dietary antioxidant index, and use of multiple vitamin supplements decreased risk for cataract. Findings from these studies suggest socioeconomic and nutritional components to cataract risk, although not consistently across studies or cataract types. Differences between studies may be due to differences in populations and/or data collection methods. Because reducing cataract risk would have major implications for a large segment of the population, clinical trials seem appropriate to confirm and evaluate the potentially modifiable risk factors suggested by these studies.

Nitric oxide synthase immunoreactivity in rat superior cervical ganglia and adrenal glands

Nitric oxide synthase-immunoreactivity (NOS-IR) was detected in strands of nerve fibers entering the rat superior cervical ganglia (SCG) and in nerve fibers forming a plexus beneath the capsule of adrenal glands. Within the SCG, varicose NOS-IR fibers encircled virtually all postganglionic neurons and small diameter cells, presumably small intensely fluorescent (SIF) cells. Perikarya of SIF cells exhibited strong NOS-IR, whereas the level appeared to be low in postganglionic neurons. Decentralization of the SCG for 4-6 days markedly reduced the number as well as the intensity of NOS-IR fibers without causing a detectable change of NOS-IR in the postganglionic neurons and SIF cells. Beneath the adrenal capsule, bundles of NOS-IR fibers bifurcated and made a sharp turn to reach the adrenal medulla. Chromaffin cells, which themselves exhibited fairly strong NOS-IR, appeared to be surrounded by NOS-IR fibers. The result shows that NOS-IR is present in pre- and post-synaptic elements of the sympathetic ganglia and adrenal medulla, representing a complex system that may regulate the activity of ganglionic neurons and chromaffin cells via a number of sites of action.

Transcriptional arrest of yeast RNA polymerase II by Escherichia coli rho protein in vitro

A promoter-independent assay utilizing poly(dC)-tailed DNA templates has revealed that Saccharomyces cerevisiae whole-cell extracts can be proficient for transcription by the endogenous yeast RNA polymerase II as well as for correct 3'-end RNA processing. Our attempts to examine the fate of polymerase II itself were inconclusive, because only trace transcription products corresponded to the expected size of terminated RNA species. Transcription in our processing-proficient extract was thus insufficient to cause termination. To test our system with a known, albeit heterologous, signal, we examined a dC-tailed template carrying the E. coli rho-dependent termination signal trp t' in the yeast extract. Transcripts from this template were not susceptible to processing, but addition of rho protein resulted in two distinct truncated transcripts that could not be chased by excess unlabeled nucleotides. These RNA species thus represented stably paused or terminated polymerase II products, and their absence when a mutated unresponsive trp t' template was used affirmed that they were due to the effects of rho. E. coli RNA polymerase added to a yeast extract pretreated with alpha-amanitin was also halted by rho at these same two sites. A mutated rho protein, while only partly defective with E. coli polymerase, failed to provoke arrest when transcription was carried out by RNA polymerase II. Thus, functional rho and its cognate site, trp t', appear necessary and sufficient to elicit the production of truncated transcripts by RNA polymerase II in a yeast whole-cell extract. The ability of rho to halt the eukaryotic enzyme strengthens the likelihood that a rho-like helicase may be involved in RNA polymerase II transcription termination.

A fluorophore-containing nitroxide as a probe to detect superoxide and hydroxyl radical generated by stimulated neutrophils

Toward the development of a fluorescence assay in combination with confocal microscopy to image free radicals generated by cells, we synthesized a fluorophore-nitroxide, 5-((2-carboxy)phenyl)-5-hydroxy-1-((2,2,5,5-tetramethyl-1-oxypyrrolid in-3- yl)methyl)-3-phenyl-2-pyrrolin-4-one sodium salt, and tested the applicability of this probe to detect oxygen-centered free radicals. The reaction of the fluorophore-nitroxide with superoxide (10 microM/min) generated either by the reaction of xanthine oxidase on xanthine or by PMA-activated neutrophils in the presence of cysteine (200 microM) resulted in a loss of electron spin resonance (ESR) signal intensity concurrent with an increase in fluorescence emission. The decrease in ESR signal and the augmentation in fluorescence emission were inhibited by the addition of superoxide dismutase. This fluorophore-nitroxide also reacted with methyl radical generated by the reaction of hydroxyl radical with DMSO (0.14 M). In this case a loss in ESR signal intensity concomitant with an increase in fluorescence emission which were inhibited by catalase (300 U/ml), was recorded. These results clearly demonstrated the feasibility of using fluorescence methodology in conjunction with a fluorophore-nitroxide to detect oxygen-centered free radicals in biological systems.

Sulfate conjugates of iodothyronines in developing sheep: effect of fetal hypothyroidism

We recently showed that thyroxine sulfate (T4S) and 3,3',5-triiodothyronine sulfate (T3S) were major thyroid hormone metabolites in ovine fetuses and neonates. To further characterize the sulfation pathway in ovine fetuses, we measured 3,3',5'-triiodothyronine (rT3S) in serum and other body fluids in samples obtained from fetal (n = 23, 94-145 days of gestational age, term = 150 days), newborn (n = 6), and adult (n = 6) sheep. In addition, T3S, T4S, and rT3S levels were measured in tissue fluids and serum samples obtained from ovine fetuses 13 days after total thyroidectomy (Tx) conducted at gestational age of 110-113 days (n = 5). Sham-operated twin fetuses served as controls (n = 5). The relative order of mean rT3S concentration for various tissue fluids in fetuses were meconium > bile > serum > allantoic fluid > urine or amniotic fluid. Peak mean tissue fluid levels generally occurred at 110-130 days gestation. In hypothyroid fetuses, significant decreases in the mean serum concentrations of T4S and rT3S, but not T3S, were noted. The mean rT3S level also was decreased significantly in allantoic fluid, bile, and meconium, whereas T4S and T3S levels were reduced only in bile of the Tx fetuses. These data demonstrate that sulfation is a major pathway in thyroid hormone metabolism in both euthyroid and hypothyroid ovine fetuses.

The development of a radioimmunoassay for reverse triiodothyronine sulfate in human serum and amniotic fluid

Sulfated iodothyronines including T4-sulfate (T4S) and T3-sulfate (T3S) have been identified in human serum and amniotic fluid. Little is known, however, about the existence of sulfate conjugation of reverse T3 (rT3S) in man. In this report, we employed a novel, sensitive, and specific rT3S RIA to address this question. The rabbit antiserum to rT3S was highly specific; T4, T3, rT3, and 3,3'-T2 showed less than 0.002% cross-reaction with the antiserum. Only T4S and T3S cross-reacted significantly (0.3% and 0.01%, respectively); other analogs cross-reacted less than 0.0001%. The detection threshold of the RIA was 14 pmol/L (1.0 ng/dL). The mean serum rT3S concentration (pmol/L) was 40 in euthyroid subjects. Values were similar in hypothyroid patients (38) and pregnant women (52) but significantly (P < 0.01) elevated to 176 in hyperthyroid patient, 74 in patients with nonthyroid illnesses, and 684 in cord sera of newborns. Serum rT3S increased significantly in hyperthyroid patients 1 day after administration of 1 g sodium ipodate orally. Reverse T3S was detected consistently in amniotic fluid at 14 to 22 weeks of gestation and showed a marked rise 1-3 weeks after intraamniotic administration of 500-1000 micrograms T4. The various data suggest that: (1) rT3S is a normal component of human serum and amniotic fluid; (2) it is derived from metabolism of T4 or rT3; (3) circulating rT3S increases in hyperthyroidism and in circumstances where type I 5'-monodeiodinating activity is low, e.g. nonthyroid illnesses, fetal life, and after administration of ipodate.

Excitatory amino acids depress synaptic currents in neonate rat sympathetic preganglionic neurons

1. Whole-cell patch-clamp recordings were made from sympathetic preganglionic neurons (SPNs) in transverse thoracolumbar spinal cord slices of 10- to 16-day-old rats, and the effects of L-glutamate (L-Glu) and analogues on excitatory (EPSCs) and inhibitory (IPSCs) postsynaptic currents evoked by stimulation of lateral funiculus were studied. 2. L-Glu (10-300 microM), quisqualate (QA, 0.1-3 microM), kainate (KA, 0.3-10 microM), ibotenate (10-25 microM), and L-2-amino-4-phosphonobutyrate (L-AP4, 25-300 microM) depressed the EPSCs and IPSCs in a concentration-dependent manner, the rank order being QA > KA > ibotenate > L-AP4 > or = L-Glu. The metabotropic glutamate receptor agonist trans-1-amino-1,3-cyclopentane-dicarboxylic acid (trans-ACPD, 25-100 microM) reduced the synaptic currents as well. A similar effect was not observed with N-methyl-D-aspartate (NMDA). 3. The excitatory amino acid uptake inhibitor L-aspartic acid-beta-hydroxamate (AAH, 100 microM), although having little or no direct effect on EPSCs, unmasked the inhibitory effect of low (< or = 1 microM) concentrations of L-Glu. 4. The synaptic depression was not accompanied by a detectable change in holding currents or EPSC reversal potentials and decay constants in the majority of SPNs studied. At higher concentrations, L-Glu and analogues, but not L-AP4, induced an inward current in some SPNs. 5. Although strongly depressing the EPSCs, L-AP4 and trans-ACPD had no significant effect on the amplitude of inward current induced by exogenous L-Glu.(ABSTRACT TRUNCATED AT 250 WORDS)

Nitric oxide synthase immunoreactivity in the rat, mouse, cat and squirrel monkey spinal cord

The distribution of nitric oxide synthase-immunoreactive neurons was examined in the spinal cord of rats, mice, cats and squirrel monkeys at the light microscopic level. Some sections were processed for choline acetyltransferase immunoreactivity. Double-labeling techniques were used to assess possible co-localization of nitric oxide synthase and choline acetyltransferase immunoreactivity in the same spinal neurons. Nitric oxide synthase-immunoreactive neurons were concentrated in three fairly well-defined regions of the spinal cord of all species studied: (i) the intermediolateral cell column of the thoracic and sacral segments, (ii) lamina X of all segments, and (iii) the superficial layers of the dorsal horn of all segments. A few nitric oxide synthase-immunoreactive neurons were scattered in the deeper laminae and the ventral horn. There were fewer nitric oxide synthase-positive neurons in monkey spinal lamina X and dorsal horn than in similar locations of rodents and felines. Double-staining showed that not all choline acetyltransferase-positive neurons in the intermediate cell column and lamina X were nitric oxide synthase-immunoreactive. In the ventral horn, choline acetyltransferase-positive neurons (presumed motoneurons) were nitric oxide synthase-negative. In addition to cell bodies, nitric oxide synthase-positive fibers were scattered in the dorsal, lateral and ventral horns of all species. Finally, punctate nitric oxide synthase-immunoreactive fibers were seen traversing the dorsal, lateral and ventral white matter, and reaching the respective gray matter. The present study shows that, in spite of quantitative differences, the pattern of distribution of nitric oxide synthase-positive neurons in the spinal cord was similar across the four species. The concentration of nitric oxide synthase-positive neurons in the autonomic nuclei and laminae I, II and X of all four species underscores a prominent role of these neurons in visceral and sensory functions.

The Lens Opacities Classification System III. The Longitudinal Study of Cataract Study Group

OBJECTIVE

To develop the Lens Opacities Classification System III (LOCS III) to overcome the limitations inherent in lens classification using LOCS II. These limitations include unequal intervals between standards, only one standard for color grading, use of integer grading, and wide 95% tolerance limits.

DESIGN AND RESULTS

The LOCS III contains an expanded set of standards that were selected from the Longitudinal Study of Cataract slide library at the Center for Clinical Cataract Research, Boston, Mass. It consists of six slit-lamp images for grading nuclear color (NC) and nuclear opalescence (NO), five retroillumination images for grading cortical cataract (C), and five retroillumination images for grading posterior subcapsular (P) cataract. Cataract severity is graded on a decimal scale, and the standards have regularly spaced intervals on a decimal scale. The 95% tolerance limits are reduced from 2.0 for each class with LOCS II to 0.7 for nuclear opalescence, 0.7 for nuclear color, 0.5 for cortical cataract, and 1.0 for posterior subcapsular cataract with the LOCS III, with excellent interobserver agreement.

CONCLUSION

The LOCS III is an improved LOCS system for grading slit-lamp and retroillumination images of age-related cataract.

[Clinical study of traditional Chinese medicine susceptible factors for senile lipid metabolic disturbance]

The syndromes among 674 cadres over 45 years in age with case-control study were investigated, and the TCM susceptible factors (TCM-SF) of senile lipid metabolic disturbance (SLMD) were analysed statistically, which indicated that Kidney-Deficiency, Phlegm-Turbid and Blood-Stasis were the main TCM-SF for SLMD. Compared with the results of presenility, it indicated that the Deficiency in origin was the intrinsic factors in development of LMD in presenile and senile period. Among which, Kidney-Deficiency possibly was the main factor. It is inferred the Deficiency in origin might cause the LMD in presenile and senile stage, and develop gradually as Syndrome of Deficiency in origin and Excess in superficiality, the latter aggravate the former as well. Both of these two Syndromes in origin affected the process of lipid metabolism. The results provided the prevention and treatment of SLMD, for further exploring the pathogenic factor and pathogenesis of the disease.

Computerized quantitative radionuclide assessment of heterotopic ossification in spinal cord injury patients

We evaluated the progression of heterotopic ossification (HO) in 17 spinal cord injury patients by comparing radiographs, quantitative radionuclide bone scans, and serum alkaline phosphatase levels. Evidence of maturation of HO appeared earlier (3 months to 6 years post injury) in radiographs, whereas, during the same time frame, radioactive nuclide assessment showed continued progression of HO in 10 out of the 17 patients. The evolution of HO appeared to take place over a period ranging between 3 and 80 months. We believe that stabilization of HO may be reasonably defined in terms of uptake ratios of 2.0 or less in patients with initial uptake ratios over 3.0 but below 5.0, and of ratios of 3.0 or less when the initial values are over 5.0.

Analysis of nuclear 3,3',5-triiodothyronine receptor in the brown adipose tissue (BAT) of the postnatal lamb

Postnatal thermogenesis in sheep is associated with increased sympathoadrenal activities, a T3 surge and an enhanced brown adipose tissue (BAT) type II 5'-monodeiodinating (5'-MDI) activity. The latter peaks 3-4 days after birth and is known to be important in generating intracellular T3 for nuclear receptor binding. In order to further investigate the mechanism(s) responsible for neonatal thermogenesis, thyroid hormone nuclear receptor (T3NR) binding characteristics were quantified in lamb BAT from newborn (NB) to 30d of postnatal age. Maximal binding capacities (MBC, mean +/- SEM fmoles T3/mg DNA) in BAT showed a decrease as studied by ANOVA during the first 11 days (NB to 1d, 148 +/- 24 [N = 5, p < 0.01, cf. 3-5d group]; 3-5 d, 61 +/- 5.5 [N = 5]; 10-11d, 72 +/- 9.1 [N = 4]). Afterwards, MBC increased at 30d (196 +/- 32, N = 4, p less than 0.01, cf. 3-5d group). BAT T3NR binding affinities (10(9) M-1) were comparable in all age groups studied (NB-1d, 2.8 +/- 0.3; 3-5d, 3.4 +/- 0.3; 10-11d, 4.0 +/- 1.1; 30d, 2.4 +/- 0.4). The data suggest that the postnatal surge in T3 and type II 5'-MDI is accompanied with a concurrent decrease in MBC of BAT T3NR. The latter may represent a down-regulation of T3NR presumably in an attempt to regulate the overall effect of thyroid hormone in neonatal thermogenesis.

Neuropathy target esterase inhibitors: 2-alkyl-, 2-alkoxy-, and 2-(aryloxy)-4H-1,3,2-benzodioxaphosphorin 2-oxides

The standard probes used earlier to study neuropathy target esterase (NTE) are N,N'-diisopropyl phosphorofluorodiamidate (mipafox), diisopropyl phosphorofluoridate (DFP), 2-(2-methylphenoxy)-4H-1,3,2-benzodioxaphosphorin 2-oxide (2-CH3C6H4O-BDPO) (the neurotoxic metabolite of tri-o-cresyl phosphate), and dipentyl 2,2-dichlorovinyl phosphate (DDP) with I50s for hen brain enzyme of 7000, 700, 29, and 3 nM, respectively. NTE phosphorylated by DFP and DDP is proposed to undergo alkylation on aging, and this probably also occurs with 2-CH3C6H4O-BDPO. Optimized probes for NTE should meet the following specifications: highest potency achievable; rapid aging perhaps associated with alkylation; preferably a phosphonate so there are only two leaving groups. An attempt was made to achieve these goals in the 4H-1,3,2-benzodioxaphosphorin 2-oxide series by synthesis of 49 analogs systematically varied in the 2-alkyl, 2-alkoxy, or 2-(aryloxy) substituent. Special precautions are required in synthesis of BDPO derivatives because of their potential hazard on human exposure. Thirty of these compounds had NTE I50s lower than 3 nM. Representative high-potency NTE inhibitors in each series are [2-substituent,I50 (nM) for hen and human brain NTE, respectively]: octyl, 0.25 and 0.18; nonyloxy, 0.89 and 0.98; 4-propylphenoxy, 0.82 and 0.77. In comparing these compounds, although the octyl analog is the most potent in vitro NTE inhibitor, the propylphenoxy compound is the most effective in vivo NTE inhibitor and delayed neurotoxicant in hens. These benzodioxaphosphorins are improved probes for investigations on NTE phosphorylation and alkylation in relation to delayed neurotoxicity.

A radioimmunoassay for measurement of 3,5,3'-triiodothyronine sulfate: studies in thyroidal and nonthyroidal diseases, pregnancy, and neonatal life

A highly sensitive, specific, and reproducible RIA has been developed to measure T3 sulfate (T3S). Only T4 sulfate cross-reacted significantly (approximately 3%) in the RIA; rT3 sulfate, T4, T3, rT3, and diiodothyronine cross-reacted less than 0.01%. T3S was bound by thyronine-binding globulin and albumin in serum. The free fraction of T3S in four normal sera averaged 0.25% compared to a value of 0.35% for T3. Therefore, T3S was measured in ethanol extracts of serum. Recovery of the nonradioactive T3S added to serum averaged 92%. The dose-response curves of inhibition of binding of [125I]T3S to anti-T3S antibody by serial dilutions of serum extracts were essentially parallel to the standard curve. The detection threshold of the RIA was 20 pmol/L (1.5 ng/dL). The coefficient of variation averaged 7.8% within an assay and 11% between assays. The serum concentration of T3S was (mean +/- SE) 76 +/- 7.2 pmol/L in normal subjects, 268 +/- 29 in hyperthyroid patients with Graves' disease, 92 +/- 28 in hypothyroid patients, 201 +/- 32 in patients with systemic nonthyroidal illnesses, 40 +/- 6.2 in pregnant women (15-31 weeks gestation), and 429 +/- 39 in cord sera of newborns; the values in hyperthyroidism, nonthyroidal illnesses, and newborns were significantly different from normal (P less than 0.01). The mean concentration of T3S in amniotic fluid samples at 15-31 weeks gestation (90 +/- 1.3 pmol/L) was significantly higher than the corresponding value in maternal serum (P less than 0.05) and significantly lower than the corresponding value in newborn cord blood serum (P less than 0.001). Oral administration of sodium ipodate (Oragrafin; 3 g) to two hyperthyroid patients was associated with a 76-190% increase in serum T3S at 8 h, followed by a gradual decrease to a nadir that was 25-60% of the baseline value 2-3 days after ipodate ingestion. We conclude that 1) T3S is a normal component of human serum, and its levels change substantially in several physiological and pathological conditions; 2) sulfation pathway plays an important role in the metabolism of iodothyronines in man; and 3) high serum T3S levels in newborns and low normal levels in pregnancy despite elevated thyronine-binding globulin levels may signify markedly different metabolism of T3S in the mother and fetus.

Metabolism of 3,5,3'-triiodothyronine sulfate by tissues of the fetal rat: a consideration of the role of desulfation of 3,5,3'-triiodothyronine sulfate as a source of T3

We have recently demonstrated that serum concentration of 3,5,3'-triiodothyronine sulfate (T3S) is markedly elevated in the human newborn at a time when serum 3,5,3'-triiodothyronine (T3) is very low. The present study explores the ability of maternal (19-21 d pregnant) and near-term fetal Sprague-Dawley rat tissues to 1) monodeiodinate T3S and T3 in both the outer and the inner ring and 2) desulfate T3S to T3. Maternal liver microsomes metabolized T3S exceedingly efficiently (compare fetus p less than 0.05). Eighty percent or more of T3S was consumed during its incubation with 360 micrograms/mL microsomes for 2 h. The majority of the consumption of T3S by adult liver microsomes occurred by its 5'-monodeiodination to I-; little inner-ring monodeiodination to 3,3'-diiodothyronine was demonstrable. In fetal liver microsomes, however, over 75% of the substrate T3S remained unchanged after a 2-h incubation. T3 was metabolized similarly moderately by fetal and maternal liver microsomes. Brain microsomes metabolized T3S poorly in both the mother and the fetus. Over 90% of substrate T3S remained unchanged after a 2-h incubation in each case. Interestingly, brain microsomes metabolized T3 more rapidly than T3S (p less than 0.05). In the fetus, desulfation of T3S to T3 was clearly evident only in microsomes from the liver and the brain; in the adult, it was plentiful in many tissues. Fetal liver and brain tissues metabolize T3S poorly, and both actively desulfate T3S to T3. These data and those indicating high serum T3S in the fetus suggest that T3S is a local source of T3 in critical tissues in the fetus and possibly in adults with the low T3 syndrome.

Synaptic mechanisms in sympathetic preganglionic neurons

Intracellular recordings from sympathetic preganglionic neurons (SPNs) in adult cat and neonatal rat spinal cord slices reveal four types of synaptic potentials, namely, excitatory postsynaptic potentials (EPSPs), inhibitory postsynaptic potentials (IPSPs), and slow EPSPs in both preparations, and a slow IPSP in cat SPNs. Pharmacological studies show that glutamate or a related excitatory amino acid and glycine are the probable mediators of EPSPs and IPSPs. There may be heterogenous mediators of slow EPSPs; substance P, serotonin, norepinephrine, and epinephrine are all probable mediators of slow EPSPs in subpopulations of SPNs. In the case of slow IPSPs, norepinephrine appears to be the likely transmitter. Finally, stimulation of ventral roots elicits a synaptic potential that appears to be caused by glutamate released from afferent fibers in the ventral roots. Our results indicate that a multitude of synaptic mechanisms exist in the rat SPNs by means of which inputs arising from sensory and supraspinal neurons are processed in a timely and orderly manner, thus ensuring highly organized but differentiated outputs to multiple peripheral target cells.

Presynaptic GABAB receptor activation attenuates synaptic transmission to rat sympathetic preganglionic neurons in vitro

Intracellular recordings were made from sympathetic preganglionic neurons (SPNs) in transverse neonate rat spinal cord slices. Superfusion of gamma-aminobutyric acid (GABA; 25-100 microM) or (-)-baclofen (1-30 microM) consistently attenuated the excitatory postsynaptic potentials (EPSPs) evoked by stimulation of dorsal rootlets or lateral funiculus, without causing a significant change of the resting membrane potential and input resistance of the SPNs or of the depolarizations induced by pressure applications of glutamate; the IC50 for baclofen was 2.5 microM. When superfused at a higher concentration (greater than or equal to 500 microM) or ejected by pressure GABA caused a bicuculline-sensitive membrane hyperpolarization. The enantiomer (+)-baclofen (10-50 microM) and the GABAA agonist muscimol (1-10 microM) had no significant effect on the EPSPs. The GABAB receptor antagonist 2-hydroxy-saclofen caused a 10 fold rightward shift of the baclofen dose-response curve, whereas the GABAA receptor antagonist bicuculline (10-50 microM) was ineffective. Glycine had no significant effects on the EPSPs in the concentrations (10-100 microM) tested here. The results indicate that of the two putative inhibitory transmitters in the spinal cord GABA but not glycine depresses EPSPs evoked in the rat SPNs by acting on presynaptic GABAB receptors, the activation of which results in a reduction of excitatory transmitter release.

Identification of thyroxine-sulfate (T4S) in human serum and amniotic fluid by a novel T4S radioimmunoassay

Recently, we identified significant amounts of thyroxine sulfate (T4S) in fetal sheep serum, meconium, bile, and amniotic and allantoic fluids. Little is known, however, about sulfate conjugation of thyroxine in humans. In this study, we employed a novel, sensitive T4S RIA to address this question. The rabbit antiserum was quite specific; T4, T3, rT3, and 3,3'-T2 showed less than 0.002% cross-reactivity. Other analogs cross-reacted less than 0.0001%. Only rT3S and T3S cross-reacted significantly (9.9% and 2.0%, respectively). The mean serum T4S concentration (ng/dL) was 8.6 in euthyroid subjects, 14.4 in hyperthyroid subjects, 5.0 in hypothyroid subjects, 5.9 in pregnancy, and 4.5 in patients with nonthyroid illnesses. T4S concentration in amniotic fluid from women at 18-19 weeks of gestation (25.5 ng/dL) was higher than that at 14-15 weeks of gestation (14.3 ng/dL). A significant rise in serum T4S was detected in hyperthyroid patients 1 day after ingestion of 1 g of ipodate. These data suggest that T4S is a normal component of human serum and amniotic fluid, and it is mostly derived from T4 peripherally and accumulates when type I 5'-monodeiodinating activity is low in fetuses or inhibited by drugs, such as ipodate.

Excitatory effects of cholecystokinin octapeptide on rat nodose ganglion cells in vitro

Cholecystokinin octapeptide (CCK-8) applied by pressure evoked in the majority of rat nodose ganglion cells a rapid depolarization associated with a fall of membrane resistance and in a few cells a slow depolarization accompanied by an increase of membrane resistance. The fast depolarizations were increased and decreased by membrane hyperpolarization and depolarization; the extrapolated reversal potential was about -10 mV. The response was depressed in a Na-free solution and by d-tubocurarine (10-100 microM) but not in a Cl-deficient solution. It is concluded that CCK-8 depolarized the nodose ganglion cells by increasing cation conductances and in a few cells it also produced a slow excitation, the mechanism of which remains to be established.

Postnatal changes in lambs of two pathways for thyroxine 5'-monodeiodination in brown adipose tissue

We have recently shown that ovine fetal brown adipose tissue (BAT) contains two distinct iodothyronine 5'-monodeiodinase (5'MDI) activities, one with a high Km (type I) and another with a low Km (type II). Both activities increased to maximum levels near term (150 days gestation). BAT plays a major role in neonatal temperature regulation in lambs, and available evidence suggests that BAT 5'MDI activity is closely linked to thermogenic capacity. To better characterize the changes in 5'MDI after birth, we studied both type I and type II 5'MDI in lamb BAT from the time of birth to 30 days of postnatal age. Type I 5'MDI activity [pmol 3,5,3'-triiodothyronine (T3).mg protein-1.h-1] showed no significant changes during the first 11 days after birth [newborn (NB), 95 +/- 16; 1 day, 83 +/- 20; 3-4 days, 80 +/- 11; 10-11 days, 92 +/- 28]. Activity decreased significantly at 30 days (24 +/- 8.9, P less than 0.05). On the other hand, the type II 5'MDI activity (fmol I- released.mg protein-1.h-1) increased significantly (P less than 0.01) during the first 4 days, (NB, 348 +/- 23; 1 day, 679 +/- 37; 3-4 days, 785 +/- 199), decreased toward NB values (401 +/- 87) at 10-11 days of age, and fell to 66 +/- 31 at 30 days (P less than 0.05 vs. NB). Kinetic analysis of BAT type II thyroxine 5'MDI revealed a rise in maximum velocity from NB to 1 and 3-4 days of age without a change in the enzymatic activity Km.(ABSTRACT TRUNCATED AT 250 WORDS)