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T Audhya

Publications and source records attributed to T Audhya.

54 records · Page 3Linked to original sources
PubMed1986

Corticotrophin-releasing factor in extra-hypothalamic brain of the mouse: demonstration by immunoassay and immunoneutralization of bioassayable activity.

Corticotrophin-releasing factor (CRF) bioactivity has been described in the extra-hypothalamic brain, but its relationship to hypothalamic CRF has remained questionable. Of the seven regions of the mouse brain examined, highest concentrations of CRF-like immunoreactivity (CRF-LI) and bioassayable CRF activity were present in the median eminence and hypothalamus. However, substantial CRF-LI and bioassayable CRF activity were also seen in brain extracts from the amygdala, thalamus, frontal cortex, pons medulla and cerebellum. Bioactivity was largely neutralized by prior incubation with heat-inactivated antiserum to ovine CRF. These findings, in conjunction with previous immunocytochemical evidence, strongly suggest that a substance closely resembling hypothalamic CRF is present in the extrahypothalamic brain of the mouse.

Amygdala↗
PubMed1985

The effects of centrally administered neuropeptides on the development of gastric lesions in the rat.

Centrally administered neuropeptides were investigated for their effects on the development of gastric lesions in rats. Thyrotropin releasing hormone (TRH), vasoactive intestinal peptide (VIP) and gonadotropin releasing hormone (LHRH) produced gastric lesions acutely, with TRH demonstrating the most pronounced effect in terms of incidence and severity. Ten-fold higher doses of the same peptides administered intravenously produced none or very few gastric lesions. Moreover, pretreatment with atropine partially inhibited their production. Corticotropin releasing factor (CRF) exhibited only mild ulcerogenic effects, and the gastric lesions induced with this peptide developed more slowly than with TRH, VIP and LHRH. Although ulcerogenic in their own right, none of these four neuropeptides significantly potentiated the potent ulcerogenic effects of cold-restraint stress. Since other neuropeptides, including somatostatin, human pancreatic growth hormone releasing factor (hpGRF), substance P, bombesin, and neurotensin, had no demonstrable effects on gastric mucosa, we can conclude that the lesions were not a general effect of intracisternal administration of neuropeptides. The results suggest that within the central nervous system, there are several neuropeptides that play a significant role in the development of gastric lesions via, at least in part, vagal-dependent mechanisms.

Animals↗
PubMed1985

Structural requirements for the biological activity of thymopentin analogs.

Thymopentin, the synthetic pentapeptide Arg-Lys-Asp-Val-Tyr, corresponds to residues 32-36 of the thymic hormone thymopoietin. Thymopentin, like thymopoietin, induces intracellular cGMP elevations in the human T-cell line, CEM. Thymopentin also displaces radiolabeled thymopoietin from a receptor glycoprotein prepared from CEM cells, provided that a nonapeptide corresponding to thymopoietin is added to block thymopoietin binding to an additional binding site. Twenty nine analogs with single position substitutions were synthesized by solid-phase or classical solution synthesis, and are evaluated in these assays. All analogs that were active gave positive effects in both assays. A number of substitutions were tolerated at positions 2, 4, and 5, but there was an absolute requirement for L- or D-Arg at position 1 and L- or D-Asp at position 3 to maintain biological activity.

Amino Acid Sequence↗
PubMed1985

Evidence for a role of endogenous corticotropin-releasing factor in cold, ether, immobilization, and traumatic stress.

The role of corticotropin-releasing factor (CRF) in four model stresses (cold, ether, immobilization, and trauma) was examined in the guinea pig by using passive immunoneutralization with anti-CRF antiserum. Plasma corticotropin levels were measured at various times after exposure to stress, and groups treated with CRF antiserum were compared with those treated with normal rabbit serum. Of the four stresses tested, ether had the most pronounced effect on corticotropin secretion. Treatment with anti-CRF inhibited most of the ether-induced corticotropin secretory response, the difference between the normal serum- and the anti-CRF antiserum-treated groups being significant at 5 and 10 min (P less than 0.01). Corticotropin responses to cold stress in the two groups differed at the 0.05 level of significance at 10 and 20 min. After administration of trauma (leg fracture), a statistically significant difference (P less than 0.01) between the two groups also was evident, albeit only at 20 min. During immobilization, corticotropin levels differed significantly from control only in the normal serum-treated group but not in the anti-CRF-treated group. These findings show that CRF antiserum was effective in reducing corticotropin levels, indicating that CRF has an important role in mediating corticotropin response to stress. The fact that neutralization was incomplete might be due to an inability of the antiserum to sufficiently neutralize the endogenous CRF or, more likely, reflects the contribution of additional mediators, notably catecholamines and vasopressin, of corticotropin release upon stress.

Adrenocorticotropic Hormone↗
PubMed1985

Levels of human and rat hypothalamic growth hormone-releasing factor as determined by specific radioimmunoassay systems.

Polyclonal antibodies to synthetic human pancreatic growth hormone-releasing factor [hpGRF(1-44)NH2] and rat hypothalamic growth hormone-releasing factor [rhGRF(1-43)OH] were produced in rabbits by injecting these weak immunogens, coupled to thyroglobulin and emulsified with complete Freund's adjuvant in the presence of activated charcoal, directly into the spleen. A subsequent booster injection by the conventional intramuscular route resulted in high-titer antibodies, which at a 1:20,000 dilution were used to develop highly sensitive and specific radioimmunoassays for these peptides. By using antibodies with an apparent Ka of 3.3 X 10(-12) (human) and 7.7 X 10(-11) (rat), the sensitivity of these assays in both human and rat was found to be less than 1 fmol. The antibody to hpGRF(1-44)NH2 is directed against the COOH-terminal region of the molecule, as shown by its crossreactivity with various hpGRF analogues: 140% with hpGRF(30-44)NH2; 1%-2% with hpGRF(1-37)OH, hpGRF(1-40)OH, and hpGRF(1-40)NH2; and none with hpGRF(1-29)NH2. Serial dilutions of human and rat hypothalamic extracts demonstrated parallelism with the corresponding species-specific standard and 125I-labeled tracer. There was no crossreactivity with other neuropeptides, gastrointestinal peptides, or hypothalamic extracts of other species. The hypothalamic content in fmol/mg (wet weight) of tissue was 3.6 +/- 0.2 for the human and 11.1 +/- 5.5 for the rat. Age-related changes in hypothalamic GRF content were present in rats, with a gradual increase from 2 to 16 weeks and a correlation between increasing body weight and GRF content. These radioimmunoassays will serve as important tools for understanding the regulation of growth hormone secretion in both human and rat.

Age Factors↗
PubMed1984

Immunoassay for bovine serum thymopoietin: discrimination from splenin by monoclonal antibodies.

A polyclonal rabbit anti-bovine thymopoietin antiserum was used to develop a radioimmunoassay and sandwich enzyme-linked immunosorbent (ELISA) assay for the thymic hormone thymopoietin. Both assays showed slightly less sensitivity for the closely related splenic hormone splenin (SP) than thymopoietin (TP) and markedly less sensitivity for the human as compared with the bovine polypeptides. A number of murine monoclonal antibodies specific for bovine thymopoietin were generated; they were unreactive with bovine splenin and were also unreactive with human thymopoietin and splenin. A sandwich ELISA using these monoclonal anti-TP antibodies together with polyclonal rabbit anti-TP was specific for bovine thymopoietin and measured 300-500 ng/ml thymopoietin in bovine serum. Similar approaches are being pursued to develop an immunoassay for thymopoietin in human serum.

Animals↗
PubMed1984

Thymopoietin radioreceptor assay utilizing lectin-purified glycoprotein from a biologically responsive T cell line.

Radiolabeled thymopoietin that was biologically active and of high specific activity was prepared by a novel technique involving protection of free amino groups, selective excision of the protected N-terminal prolyl group with post-proline cleaving enzyme, reaction of the newly exposed alpha-amino group with a highly radioiodinated compound, and deprotection and purification of the polypeptide. Binding of this radiolabeled thymopoietin was not demonstrable by conventional techniques with cells, cell membranes, or solubilized cell membranes, apparently due to the presence of active proteases in these preparations. A glycoprotein with thymopoietin binding properties was prepared by lectin purification from the detergent-solubilized membranes of CEM cells, a human T cell line that responds to thymopoietin in vitro with increases in intracellular cyclic GMP. Presumably this procedure separated the thymopoietin binding protein from membrane proteases, thus permitting the development of a radioreceptor assay. Evidence is presented that the thymopoietin binding protein represents a thymopoietin receptor that is probably related to the mediation of immunoregulatory actions of thymopoietin on a subset of peripheral T cells.

Binding, Competitive↗
PubMed1984

Cooperativity of thymopoietin 32-36 (the active site) and thymopoietin 38-45 in receptor binding.

Thymopoietin is a 49 amino acid polypeptide hormone of the thymus whose biological activity is reproduced by the synthetic pentapeptide thymopentin, corresponding to amino acids 32-36. Thymopentin requires the addition of an octapeptide corresponding to thymopoietin 38-45 for full competition with native thymopoietin in a radioreceptor assay with receptor derived from the human T-cell line CEM. Thus thymopoietin appears to bind to its receptor on T-cells by two regions (32-36 and 38-45). Thymopentin alone is biologically active and induces elevations of intracellular cyclic GMP. Whilst occupancy of the adjacent site by thymopoietin 37-45 does not of itself cause an elevation of intracellular cyclic GMP this peptide is not biologically silent as it does enhance the potency of thymopentin.

Amino Acid Sequence↗
PubMed1984

Contrasting biological activities of thymopoietin and splenin, two closely related polypeptide products of thymus and spleen.

Thymopoietin, a 49 amino acid polypeptide hormone of the thymus discovered by its effect on neuromuscular transmission, was later shown to induce T-cell differentiation and to affect immunoregulatory balance. A radioimmunoassay for thymopoietin revealed a crossreaction with a product found in spleen and lymph node but not other tissues. This product, named splenin, differs from thymopoietin only in position 34, aspartic acid for bovine thymopoietin and glutamic acid for bovine splenin. Synthetic pentapeptides corresponding to residues 32-36, called thymopentin and splenopentin, reproduce biological activities of thymopoietin and splenin, respectively. Thus thymopoietin and thymopentin affect neuromuscular transmission and induce the phenotypic differentiation of T precursor cells in vitro while inhibiting phenotypic differentiation of B cells. Splenin and splenopentin, in contrast, do not affect neuromuscular transmission, and they induce both T- and B-cell precursors.

Amino Acid Sequence↗
PubMed1983

Comparative efficacy of various routes of administration of thymopentin (TP-5) with consideration of degradative mechanisms.

Thymopoietin (originally termed TP-5 and now called thymopentin) is a synthetic pentapeptide that can reproduce the biological activity of the 49 amino acid thymic hormone thymopoietin. The efficacy of various routes of administration of thymopentin was studied in mice and guinea pigs using an electromyographic assay as an end point to determine biological activity. In mice, the threshold dose necessary for a significant response when compared to controls was 0.03 mg/kg (mpk) for i.v. (intravenous) injection and 0.3 mpk for both i.p. (intraperitoneal) and s.c. (subcutaneous) injection. For the guinea pig, 0.03 mpk produced a significant response when compared to controls when injected either i.v. or s.c.; 0.3 mpk was required for a significant response for i.n. (intranasal) administration and 0.6 mpk for i.p. injection. When saline or plasma was injected, it produced no change in the electromyographic response. In plasma the pentapeptide is rapidly degraded by proteolytic enzymes. Treatment of plasma with specific enzyme inhibitors followed by incubation with thymopentin or thymopoietin confirmed that serine protease and aminopeptidase M-like enzymes are responsible for the rapid inactivation of thymopentin in plasma, as measured by the electromyographic response.

Animals↗
PubMed1983

Thymopentin (TP-5) potency in vivo is enhanced by slow infusion.

The in vivo activity of thymopentin in guinea pigs was assessed electromyographically 18 h after intravenous or subcutaneous injections or infusions ranging over varying periods of time. The lowest threshold dose required to establish a positive effect was obtained with a 30-60 min i.v. infusion (0.38-0.75 micrograms/kg) and we found that we needed X 5 times this dose with 30 min s.c. infusion, X 10 this dose with 10 min i.v. or s.c. infusion, X 200 this dose with bolus IV injection and X 400 this dose with bolus s.c. injection. The marked increase of potency of thymopentin with infusion should be considered in designing clinical regimens.

Animals↗
PubMed1983

Levels of corticotropin releasing factor-like immunoreactivity in mammalian hypothalamic and extrahypothalamic brain tissue as determined with a monoclonal antibody to the ovine material.

A monoclonal antibody to ovine corticotropin releasing factor (CRF) has been produced by fusion of a non-producing plasmacytoma cell line P3U1 with spleen cells of Balb/c mice immunized with the synthetic 41 amino acid peptide coupled covalently with rabbit myosin by a heterobifunctional reagent, N-succinimidyl 3-(2-pyridyldithio) propionate. A total immunizing dose of 500 micrograms resulted in a highly specific, high-affinity antibody with a Ka of 0.15 x 10(12) M-1, which was used to establish a specific RIA with a sensitivity of 10 pg/tube. Levels of corticotropin releasing factor-like immunoreactivity (CRF-LI) in a pg/mg of hypothalamic tissue ranged from 4-10 in ovine, 2.5-8 in bovine, 47.5-67.5 in mouse and 2.3-20 in human tissue. Moreover, CRF-LI was widely distributed in extrahypothalamic mouse brain at concentrations approximately one half those seen in hypothalamus.

Amygdala↗
PubMed1983

Distribution, biosynthesis, and physiological role of corticotropin-releasing factor in the human: an overview.

Our findings to date indicate that: A peptide resembling oCRF is present in human and mammalian hypothalamus. oCRF is present in human lumbar cerebrospinal fluid. oCRF concentrations do not differ in CSF from normal individuals and from patients with Cushing's syndrome. oCRF appears to be synthesized via a large oligopeptide precursor. An oCRF-like molecule (oCRF-LI) is present in hypothalamic brain tissue. We have also observed more tentative evidence of low levels of oCRF-LI outside of the brain. oCRF is likely to be a central mediator of stress in its multiple forms. We believe that oCRF is clearly of major physiological importance, but that many critical unanswered questions remain. Probably, the most fascinating of these, which we are only beginning to comprehend, concerns the functions of CRF in extrahypothalamic brain as well as the CRF which appears to be present outside the brain.

Animals↗
PubMed1981

Complete amino acid sequences of bovine thymopoietins I, II, and III: closely homologous polypeptides.

Complete amino acid sequences were determined for thymopoietins I and II (revision), isolated from bovine thymus, and for thymopoietin III, a newly identified polypeptide isolated from bovine spleen. Thymopoietin III (TP-III) is a 49 amino acid monomeric peptide that shows minor microheterogeneity at residue 34. The three thymopoietins have largely identical sequences yet some distinct differences, suggesting very recent evolution from a common gene. The complete amino acid sequences are (Formula: see text).

Amino Acid Sequence↗
PubMedDate not supplied

Selected human T cell lines respond to thymopoietin with intracellular cyclic GMP elevations.

Ten established human cell lines were tested for their responsiveness to thymopoietin by measuring their intracellular cyclic nucleotide levels. Three T cell lines (CCRF-CEM, MOLT-4 and CCRF-HSB-2) responded to thymopoietin with elevations of intracellular cGMP but not cAMP; seven other human cell lines did not respond to thymopoietin (three T cell lines, three B cell lines and one erythropoietic stem cell line). Interestingly, only one cell line (MOLT-4) was also responsive to the closely related polypeptide splenin, and this reactivity was restricted to human and not bovine splenin. The detection of human cell lines with distinctive patterns of response to immunoregulatory peptides should provide support for understanding the immunopharmacological mechanisms by which these molecules act.

Cell Line↗
PubMedDate not supplied

Biologically active analogs of thymopentin with enhanced enzymatic stability.

Thymopentin, a synthetic pentapeptide fragment of thymopoietin (residues 32-36, Arg-Lys-Asp-Val-Tyr) is biologically active but susceptible to proteolytic digestion. Analogs were synthesized and studied for biological activity and susceptibility to peptidases. Amino acid changes were incorporated at positions known to not affect activity adversely and N-terminal acetylation and C-terminal amidation were used to increase resistance to proteolytic degradation by exopeptidases. Ac-Pro2-TP5-NH2 and Aib2-TP5-NH2 retained activity and were shown to exhibit a high degree of stability when incubated in human serum.

Cell Line↗
PubMedDate not supplied

Abnormally high plasma levels of vitamin B6 in children with autism not taking supplements compared to controls not taking supplements.

BACKGROUND: There have been many studies of the effect of high-dose supplementation of vitamin B6 on children and adults with autism, with all but one reporting benefits. OBJECTIVE: The aim of this study was to investigate the biochemical basis for vitamin B6 therapy by measuring the level of total vitamin B6 in the plasma of unsupplemented children with autism spectrum disorder compared to unsupplemented control subjects. PARTICIPANTS: Children with autism spectrum disorders (n = 35, age 3-9 years) and unrelated typical children (n = 11, age 6-9 years), all from Arizona, were studied. (This includes the data from 24 children with autism from our previous study.) METHODOLOGY: A microbiologic assay was used to measure the level of total vitamin B6 (including phosphorylated and unphosphorylated forms), in a blinded fashion. RESULTS: Children with autism had a 75% higher level of total vitamin B6 than the controls (medians of 56 versus 32 ng/mL, respectively, p = 0.00002). Most of the autistic children (77%) had levels that were more than 2 standard deviations above the median value of the controls. The autistic girls (n = 5) also had elevated levels (mean of 54.6 ng/mL, median of 60 ng/mL). DISCUSSION: These results are consistent with previous studies that found that: (1) pyridoxal kinase had a very low activity in children with autism and (2) pyridoxal 5 phosphate (PLP) levels are unusually low in children with autism. Thus, it appears that the low conversion of pyridoxal and pyridoxine to PLP results in low levels of PLP, which is the active cofactor for 113 known enzymatic reactions, including the formation of many key neurotransmitters. CONCLUSIONS: Total vitamin B6 is abnormally high in autism, consistent with previous reports of an impaired pyridoxal kinase for the conversion of pyridoxine and pyridoxal to PLP. This may explain the many published studies of benefits of high-dose vitamin B6 supplementation in some children and adults with autism.

Autistic Disorder↗