Postmenopausal estrogen therapy and cardiovascular disease.
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Coronary Disease↗
Biomedical subjects
D B MacLean
Publications and source records attributed to D B MacLean.
Weight loss induced by gastric implant in rats. Effects of capsaicin sensory denervation.
To study the efficacy and mechanism of action of the intragastric bubble, 1- to 5-ml silicone bubbles were surgically implanted into the stomachs of 10- to 12-week-old female rats. To test the hypothesis that the satiety effects of the implant are mediated by visceral sensory nerves, a subgroup was treated as neonates with the sensory neurotoxin capsaicin, 50 mg/kg subcutaneously. In control animals, the implants caused a transient decrease in body weight, compared to sham-implanted animals, most evident at three days and abolished by 18 days after operation. In contrast, capsaicin-treated animals did not lose weight in response to gastric implantation. Substance P was decreased in the vagus nerves of capsaicin-treated animals, confirming sensory denervation. At autopsy, all gastric implanted rats had enlarged stomachs. We conclude that intact sensory innervation is essential for weight loss in response to the gastric bubble.
Animals↗
Determination of the glycosidic linkage in peracetylated disaccharides comprised of D-glucopyranose units by use of desorption electron-ionization mass spectrometry.
An oxonium ion at m/z317 is present in the desorption electron ionization and ammonia desorption chemical ionization mass spectra of peracetylated disaccharides, comprised of glucopyranose units linked (1-->2), (1-->3), (1-->4) and (1-->6), but is absent in the spectra of the (1-->1)-linked isomer. The ion at m/z317, which is derived from the reducing moiety, has an O-formyl group at the position of linkage to the non-reducing moiety, and O-acetyl groups at each of the remaining positions. The isomeric monoformyl, triacetyl oxonium ions (at m/z317), derived from the (1-->2)-, (1-->3)-, (1-->4)- and (1-->6)-linked disaccharides, give distinctly different mass-analysed ion kinetic energy spectra, thereby enabling the linkage position to be assigned unambiguously.
Acetylation↗
In situ hybridization of preprotachykinin mRNA in cultured vagal sensory neurons. The effect of nerve growth factor.
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Animals↗
Reduction of azides under conditions of desorption-chemical ionization or fast-atom-bombardment mass-spectrometry.
Under conditions of desorption-chemical ionization or fast-atom-bombardment mass-spectrometry, the azido groups in some carbohydrate derivatives and other substances undergo apparent reduction to amino groups. Experimental evidence is provided to corroborate the reduction, and possible explanations are proposed for the phenomenon.
Ammonia↗
Basal and stimulated release of substance P from dissociated cultures of vagal sensory neurons.
Substance P, the widely distributed 11 amino acid neuropeptide, is present in up to 20% of vagal sensory cell bodies and the fibers emanating from them. To study the factors regulating the release of SP, vagal sensory (nodose or nodose/jugular) ganglia were obtained from neonatal rats and dissociated using neutral protease. Survival of plated neurons on collagen substrate was 10-20% at 2 weeks and 20-30% when neurons were plated over previously dissociated rat atriacytes. Substance P content was low in cultures for the first several days, then rose linearly to 0.1-0.2 pg/surviving neuron. Substance P was released into a 4.5 mM potassium medium at a steady rate of 0.036%/min. In 50 mM K+ supplemented medium, total release during 20 min increased 5-8-fold and steady-state release increased 4-5-fold to 0.15%/min. The sensory neuron specific excitatory neurotoxin, capsaicin, evoked SP release in similar amounts to 50 mM K+. Both net K(+)- and capsaicin-evoked, but not basal release were completely inhibited by 3.5 mM cobalt chloride. Bradykinin, 1-100 nM, stimulated SP release 2-4 times above basal levels. Forskolin and phorbol ester also increased SP release 1.5-3 times basal amounts. In summary, substance P is present in cultured vagal sensory neurons in amounts similar to in vivo and is released in response to sensory specific stimuli. These cultures should allow exploration of some of the tissue specific factors regulating neurotransmitter release in the sensory vagus nerve.
Animals↗
Herpes zoster infection of the chest wall and the syndrome of inappropriate antidiuretic hormone secretion.
The syndrome of inappropriate antidiuretic hormone secretion (SIADH) can result from diverse conditions. There have been only two published reports linking this syndrome with herpes zoster infections--one disseminated and the other confined to the chest wall. We have reported a case in which herpes zoster infection of the chest wall probably precipitated the development of this syndrome.
Aged↗
Differential regulation of calcitonin gene-related peptide and substance P in cultured neonatal rat vagal sensory neurons.
Nodose (inferior vagal sensory) ganglia were removed from neonatal rats, enzymatically dispersed using neutral protease, and maintained on previously dispersed rat atriacytes. After 7-10 days in culture, calcitonin gene-related peptide (CGRP) was present in 1-3 times the molar amount of substance P (SP). The content of SP was doubled by the addition of nerve growth factor (NGF) whereas CGRP was significantly less increased by 50% or less. The addition of forskolin increased SP and CGRP levels in cultures with or without NGF by 60-80 percent. Phorbol ester (PMA) did not alter SP content but significantly raised CGRP content by 40% in NGF supplemented cultures (P less than 0.001). Corticosterone, 0.01-0.1 microM, reduced SP content by 30% independently of NGF but had no effect on CGRP. These studies demonstrate that SP in vagal sensory neurons is more sensitive than CGRP to the effects of NGF or corticosterone. Both peptides are up-regulated by presumed increases in intracellular cyclic AMP, while CGRP (or CGRP neurons) may be independently regulated by protein kinase C.
Animals↗
Effects of a gastric implant on body weight and gastrointestinal hormones in cafeteria diet obese rats.
In order to evaluate the effectiveness of a gastric implant in an animal model of dietary obesity, silicone implants (2.5 ml) were inserted into the stomachs of male rats maintained on a chow or "cafeteria" diet. At the time of implantation, the cafeteria fed rats weighed 14% more than chow fed controls. Overweight cafeteria fed animals lost weight in response to the gastric implant, whereas control chow fed animals did not. Both implant groups had significant increases in stomach weights in contrast to sham implant groups, but the increase was much less in the cafeteria diet group. The fasting plasma levels of the gastrointestinal hormones, gastrin and pancreatic polypeptide, and oxytocin (a marker of vagal afferent function) were measured by radioimmunoassay. Cafeteria fed sham or implanted animals had significantly higher fasting levels of plasma oxytocin and gastrin, and significantly lower plasma levels of pancreatic polypeptide than the chow fed groups. These studies demonstrate that the gastric implant has more effect on weight in overweight animals on a palatable mixed diet, perhaps related to both mechanical and neural factors.
Animals↗
Substance P content in cultured neonatal rat vagal sensory neurons: the effect of nerve growth factor.
To begin to study the factors regulating the synthesis and release of substance P (SP) in the sensory vagus nerve, cultures of neonatal rat nodose ganglia were developed. In microexplant cultures, obtained from small fragments of nodose ganglia, SP was present in low amounts: after 3 weeks, 141 +/- 36 pg per well, 10 ganglia equivalents per well. To enhance neuron survival, nodose ganglia were enzymatically dissociated using neutral protease. Estimated survival at 5 days was 20-30%, with 800-1200 surviving neurons per plated ganglion, and decreased slowly thereafter. Specific SP immunostaining was present in 10-20% of neurons, mostly of small diameter (18-22 micron). SP content was low for 5 days then rose progressively after 14 days to 80-150 pg per plated ganglion. The addition of nerve growth factor (NGF, 100 ng/ml) to the culture medium did not alter neuron survival. However, SP content was doubled in the presence of NGF, or fell rapidly to one-half control levels following its withdrawal: e.g. following 12 days in culture with NGF 1185 +/- 176 pg/well vs NGF withdrawn day 8-12, 592 +/- 118 pg/well, mean +/- S.D., P less than 0.01. Somatostatin, present in one-sixth the amount of SP, was unaltered by NGF. In subsequent studies, plating of neurons onto previously dissociated rat atriacytes increased survival by 50% but did not alter SP content per surviving neurons. These studies demonstrate that SP is present in dissociated cultures of rat vagal sensory neurons; the quantities and estimated net synthesis rate correspond to previous observations in vivo. The studies also demonstrate that SP content but not neuron survival are regulated by NGF in nodose ganglion neurons. This model may prove valuable for the study of SP and other sensory neuropeptides in this important class of visceral afferent neurons.
Animals↗
Substance P synthesis and transport in explants of nodose ganglion/vagus nerve: effects of double ligation, 2-deoxyglucose, veratridine, and ouabain.
Substance P (SP), the widely distributed undecapeptide, is synthesized in cell bodies of vagal sensory ganglia and transported bidirectionally toward the CNS and thoracic and abdominal viscera. In explants of the guinea pig inferior (nodose) vagal sensory ganglion and attached 2 cm of distal vagus nerve, SP is synthesized within the ganglion and transported predominantly distally. The quantity of distal transport is similar to that observed in vivo and provides an index of ongoing synthesis within the ganglion. In this report, the model is further characterized. Double ligation of the explant distal to the ganglion demonstrates that all the transported peptide is derived from the ganglion; there is no evidence of intraaxonal processing of peptide precursor. Approximately 50% of the peptide is in a rapid transport vs. an apparent stationary compartment. Not only transport, but also synthesis, of SP was blocked by 20 mM colchicine. Ongoing SP biosynthesis is dependent on a nutrient medium [medium 199 (M-199)] and is partially inhibited with added fetal bovine serum (FBS; 10%): total explant content in M-199/FBS vs. M-199, 1,785 +/- 101 (n = 8) vs. 2,254 +/- 123 pg (n = 9); p less than 0.02. Addition of 2-deoxyglucose (2-DG) decreased both total SP synthesis and transport (total explant content for 2-DG vs. control, 986 +/- 94 vs. 1,391 +/- 111; p less than 0.05). Medium supplemented with glucose to a final concentration of 600 mg/100 ml or with glucose (300 mg/100 ml) with or without insulin (50 ng/ml) did not alter explant SP content or transport. Veratridine (5 X 10(-6) M) inhibited both SP synthesis and transport; ouabain (10(-4) M) also inhibited synthesis, but less so transport. Tetrodotoxin reversed the effects of veratridine. These studies demonstrate the usefulness of this model, which can examine factors regulating both synthesis and transport of sensory neuropeptides in vitro. The results suggest that SP synthesis/transport may be under tonic inhibition, perhaps by both neural and humoral mechanisms.
Animals↗
Adrenocorticotropin-adrenal regulation of transported substance P in the vagus nerve of the rat.
The factors regulating substance P (SP) synthesis and quantity of transport in the sensory vagus nerve are unknown. To examine this issue rats were administered ACTH or corticosterone or subjected to adrenalectomy, and the quantity of peripherally directed transported SP was measured in those animals as an indication of neuropeptide synthesis. ACTH treatment (12 U/day, sc, for 14 days) resulted in significant adrenal hypertrophy and increased corticosterone levels. The 24-h accumulation of SP proximal to ligature in the cervical vagus was significantly reduced [mean net proximal segment content: controls, 529 +/- 42 (+/- SEM) pg/3 mm segment; ACTH, 282 +/- 44]. The content in the unligated nerve, one sixth or less than that proximal to ligature, was not different in the two groups. In a separate experiment, ACTH (6 U/day for 14 days) had no effect compared to controls, whereas 16 U/day reduced transported SP. The content in the unligated nerve was again not different in the two groups. In the same experiment, corticosterone (2.5 mg/100 g BW, sc, for 14 days) reduced the quantity of transported SP. Total protein content in proximal segments was reduced only in the corticosterone group and was identical in all groups in unligated nerve. Adrenalectomy modestly increased transport by 20% and contralateral unligated nerve content by a similar percentage. The quantity of transported somatostatin, another vagal neuropeptide partly derived from sensory cell bodies, was either increased or unaltered by the experimental manipulations. In summary, these studies demonstrate that the chronic administration of ACTH or corticosterone significantly decreases the quantity of peripherally transported SP in the sensory vagus nerve and, presumably, synthesis within the vagal sensory ganglia. Down-regulation of synthesized/transported neuropeptide suggests a mechanism by which the ACTH-adrenal axis, acting through visceral sensory nerves, may modulate autonomic or central nervous system vagally mediated reflex arcs.
Adrenal Glands↗
Substance P and somatostatin content and transport in vagus and sciatic nerves of the streptozocin-induced diabetic rat.
Substance P (SP) and somatostatin (SS) are two widely distributed neuropeptides that within the vagus and sciatic nerves are localized predominantly in sensory fibers. The effect of diabetes mellitus on their content or transport in sensory nerves is unknown. With the nerve ligation technique, the peripheral orthograde 24-h transport of both peptides was quantified in the vagus nerve 3 days or 1 mo after induction of streptozocin (STZ) diabetes and in both the vagus and sciatic nerves after diabetes of 3 mo duration. In acute (3-day) diabetics, neuropeptide transport in the vagus was unaltered. After 1 mo, SP transport was significantly increased; content in unligated contralateral nerve was unaltered. Transport of SS was unchanged, and content in contralateral nerve was too low to reliably quantitate. After diabetes of 3-mo duration, transport of both peptides in the vagus nerve was increased in STZ-induced diabetic (STZ-D) rats versus both weight- and age-matched controls: SP 474 +/- 17 (N = 10) vs. 358 +/- 32 (N = 13) pg/24 h, STZ-D rats vs. controls, mean +/- SE, P less than .03; SS 29 +/- 4 vs. 20 +/- 3 pg/24 h, STZ-D rats vs. controls, P less than .02. In the sciatic nerve, SP transport and content were unaltered. SS content was significantly reduced: 17 +/- 3 vs. 30 +/- 3 pg/3-mm nerve segment, STZ-D rats vs. controls, P less than .01. SS transport in the sciatic nerve of diabetic rats was variably reduced (P less than .07), and transport rates were increased (1.41 +/- 0.13 vs. 0.96 +/- 0.10 mm/h.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Abrogation of peripheral cholecystokinin-satiety in the capsaicin treated rat.
Cholecystokinin (CCK) is a peripheral and central mediator of short-term satiety. When given i.p., CCK decreases food intake in previously fasted rats for a period of 30 min. The effect has been previously shown to be abolished by vagotomy and more specifically by severing of vagal sensory rootlets. These studies were designed to determine the effects on rat feeding behavior, and in particular CCK-satiety, of the sensory neurotoxin capsaicin. In neonates, capsaicin selectively and permanently destroys unmyelinated sensory fibers including those in the vagus nerve. Rat neonates were treated with capsaicin, 50 mg/kg or vehicle, and surviving females studied at 8-10 weeks of age. The weights, 24-h food intake, and feeding responses to insulin were the same in adult capsaicin treated (Cap Rx) and vehicle treated (Veh Rx) rats. CCK (8 micrograms/kg i.p.) reduced 30 min food intake 61 +/- 18% in Veh Rx animals (mean +/- S.D., P less than 0.01). In capsaicin denervated animals, CCK also significantly reduced 30 min food intake from 5.09 +/- 1.10 to 3.92 +/- 0.84 g (P less than 0.01), but the mean reduction, 23 +/- 6%, was significantly less than in Veh Rx rats (P less than 10(-4]. A separate group of females, similarly treated as neonates with capsaicin or vehicle, were subjected to bilateral lesioning of the ventromedial hypothalamus. Both Cap Rx and Veh Rx animals gained significantly and equally more than non-lesioned controls. 24 h vagal transport of substance P was reduced 70% in age matched capsaicin treated animals compared to controls. These studies demonstrate that peripheral CCK-satiety is partly mediated by capsaicin sensitive fibers, presumably in the vagus nerve. Substance P is one possible transmitter mediating this reflex. Further conclusions are that active inhibition of an intact peripheral CCK-stimulated reflex arc is not necessary for full expression of central inducers of feeding, e.g., insulin or lesioning of the ventromedial hypothalamus, and that destruction of these fibers does not alter long-term weight regulation in rats receiving a normal diet.
Aging↗
De novo synthesis and axoplasmic transport of [35S]methionine-substance P in explants of nodose ganglion/vagus nerve.
The synthesis and transport of substance P, the widely distributed undecapeptide, was studied in the vagus nerve of the guinea pig. In preliminary in vivo studies, the cervical vagus nerve was ligated 2 cm distal to the nodose ganglion. Twenty-four hours later, the content of immunoreactive substance P (IR-SP) in the 3-mm nerve segment proximal to ligature was 2147 +/- 207 pg (mean +/- S.E.M.) vs 133 +/- 31 pg in an equal segment of unligated nerve or 243 +/- 55 pg in the nodose ganglion. When the vagus nerve was crushed above the ganglion and simultaneously ligated 2 cm distally, the IR-SP content proximal to the ligature was reduced 50% to 1131 +/- 99 pg (P less than 0.01), while nodose ganglion content increased to 420 +/- 140 pg (n.s.). To confirm that residual transport following supranodose crush was derived from nodose ganglion-synthesized SP, SP synthesis and transport were studied in explants of nodose ganglion and attached distal vagus nerve removed from perfused animals and maintained in vitro for up to 24 h. At the time of resection, nerves were ligated 1.5 cm distal to the ganglion. Twenty-four hours following explantation, IR-SP content in proximal segments was 1022 +/- 142 pg vs 155 +/- 22 pg in unligated segments and 560 +/- 72 pg in the nodose ganglion. Accumulation in the proximal segment was time dependent. In separate experiments, [35S]methionine was added to explant medium and the explants maintained for varying time intervals. Nerve tissue was extracted and subjected to either serial reverse phase high performance liquid chromatography (HPLC), or immunoprecipitation with SP antiserum followed by a single HPLC separation. By 4 h, radiolabeled SP was present in nodose ganglia and lesser amounts in the proximal segments. By 12 h, [35S]SP was present equally in ganglia and proximal segments whereas by 18 h, two-thirds or more of the newly synthesized peptide was present in proximal segments. At 18 h, the quantity of radiolabeled SP covaried with IR-SP content in the individual nerve segments. The addition of cycloheximide to explant medium reduced [35S]SP synthesis by 90%. These studies demonstrate that: (1) approximately 50% of immunoreactive SP transported efferently within the vagus nerve of the guinea pig is derived from the nodose ganglion, (2) de novo SP synthesis within and export from the nodose ganglion occurs within 4 h, (3) the changes in IR-SP content demonstrated in in vivo and in vitro ligation studies accurately reflect ongoing SP synthesis within the nodose ganglion.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Axoplasmic transport of somatostatin and substance P in the vagus nerve of the rat, guinea pig and cat.
The axoplasmic transport of somatostatin (SS) and substance P (SP) in the cervical vagus nerve was studied in the rat, guinea pig and cat. In preliminary studies, neuropeptide immunoreactivity (IR-SS and IR-SP) was evaluated in extracts of nodose ganglion and vagus nerve using gel and reverse-phase high-performance liquid chromatography (HPLC). In each species, a single immunoreactive form of SP co-eluted with the synthetic undecapeptide on a Bio-Gel P-10 column. More than 95% of transported vagal IR-SS co-eluted with synthetic SS-14. A small percentage in each species co-eluted with SS-28. No larger form, corresponding to a prosomatostatin, was identified in any of the 3 species. On HPLC, IR-SP and IR-SS co-eluted with their synthetic forms. To quantify neuropeptide transport, the vagus nerve was ligated distal to the nodose ganglion. 24 h later in each species, the content of IR-SS and IR-SP was more than 6 times greater in a 3-mm segment of nerve proximal to the ligature than in equal length segments distal to ligature or in the unligated contralateral nerve. In the proximal segment, the net content of IR-SP (pg/3-mm segment, mean +/- S.E.M.) was 366 +/- 45 in the rat, 2038 +/- 184 in the guinea pig, and 912 +/- 108 in the cat. The content of IR-SS in the same segment was 36 +/- 4, 66 +/- 13, and 575 +/- 59 pg/3-mm, respectively. The apparent transport velocities were similar for each peptide and among species. The contribution of the nodose ganglion to transported neuropeptide was estimated by crushing the vagus above the nodose ganglion and simultaneously ligating the nerve distal to the ganglion. The percent contribution of the ganglion to transported IR-SS following this procedure was 50% in the rat, 73% in the guinea pig, and 16% in the cat. Nodose ganglion contribution to IR-SP transport was 31%, 50% and 74%, respectively. Estimated turnover of IR-SS and IR-SP within the ganglion ranged from 4.1 to 6.8 times per 24 h in each species.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Studies of the axoplasmic transport of somatostatin in the vagus nerve of the rat.
These studies were performed to examine the axoplasmic transport of somatostatin (SS) in the cervical vagus nerve of the rat. As a preliminary step, the immunoreactive SS (IR-SS) obtained from extracts of the vagal nodose ganglion and the vagus nerve was subjected to chromatographic analysis. On a Bio-Gel P-10 column, 92% of the nodose ganglion IR-SS and 98% of the vagal IR-SS coeluted with synthetic SS-14. The remaining immunoreactivity in both areas coeluted with synthetic SS-28. Vagal IR-SS demonstrated migratory characteristics identical to those of synthetic SS-14 on high performance liquid chromatography. A larger molecular weight form of IR-SS, which may correspond to prosomatostatin, was not identified in either site. When the vagus nerve was ligated distal to the nodose ganglion, the content of IR-SS increased in a time-dependent manner in the 3-mm segment of nerve proximal to the ligature. No increase in IR-SS was observed in an equal segment of nerve distal to the ligation or in the unligated contralateral nerve. Twenty-four hours after the ligation, the content of IR-SS (picograms per 3 mm; mean +/- SD) was: proximal segment, 33.9 +/- 9.6; distal segment, 3.4 +/- 3.0; and contralateral nerve, 1.7 +/- 0.7. The apparent transport velocity of IR-SS was estimated to be 2.1 +/- 1.5 mm/h. A variety of experimental approaches were used to characterize the mechanisms underlying the transport process and to define the anatomical sites of origin of the transported peptide. The application of colchicine to the vagus nerve resulted in an accumulation of IR-SS above the area which was not significantly different from that obtained after nerve ligation. When the vagus nerve was crushed above the nodose ganglion, the accumulation of IR-SS in the proximal segment was reduced by 50%, although the IR-SS content in the nodose ganglion and in the intervening nerve segments was unchanged by this procedure. The induction of a chemical sympathectomy with guanethidine had no effect on the accumulation of IR-SS. The administration of capsaicin during the neonatal period or in adult life had no effect on the transport of IR-SS, but greatly decreased the transport of substance P.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Normal immunoregulation of in vitro antibody secretion in autoimmune thyroid disease.
Defective suppressor cell function may be a causative factor in autoimmune disease in animals and man. In autoimmune thyroid disease, decreased suppressor cell activity could, under appropriate conditions, account for excess production of thyroid autoantibodies. We evaluated suppressor cell function in patients with Graves' disease and Hashimoto's thyroiditis and in normal controls. The method used is based on the principle that immunoglobulin synthesis by pokeweed mitogen (PWM)-stimulated lymphocytes is inhibited by Concanavalin A (Con A) stimulation of suppressor T cells. We studied suppressor cell control of polyclonal immunoglobulin G (IgG) and the thyroid-specific autoantibody, antimicrosomal antibody. PWM-stimulated IgG secretion (mean +/- SD) by lymphocytes from patients with Graves' disease (2797 +/- 718 ng/ml) and Hashimoto's thyroiditis (2201 +/- 423 ng/ml) did not differ from normal subjects (2431 +/- 485 ng/ml). The addition of Con A to PWM-stimulated lymphocytes suppressed IgG production in all three groups: Graves', 475 +/- 137 ng/ml; Hashimoto's, 507 +/- 74 ng/ml; and normal subjects, 460 +/- 156 ng/ml. The degree of suppression by the disease groups did not differ from the normal controls. Antimicrosomal antibody was detected in the concentrated, PWM-stimulated culture media of two of four Hashimoto's lymphocytes, three of five Graves' lymphocytes, and none of nine normal controls. Con A induced marked suppression of this organ-specific antibody in all cases. We conclude that Con A-stimulated lymphocytes from patients with Hashimoto's thyroiditis and Graves' disease can suppress antimicrosomal antibody and polyclonal IgG synthesis. These findings do not support the postulate of a generalized defect of suppressor cell function in these thyroid disorders.
Adult↗