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Biomedical subjects

T J O'Brien

Publications and source records attributed to T J O'Brien.

At least 145 records · Page 8Linked to original sources
PubMed1978

Developmental restrictions on hormone modulated gene transcription. II. Hormone induced interactions of RNA polymerase with chromatin.

Chromatin-bound and soluble RNA polymerase subspecies have been isolated and fractionated by isoelectric focusing at various times (0, 6, 12 and 18 h) following auxin treatment of 4 day (responsive) and 8 day (unresponsive) soybean hypocotyls. Young 4 day seedlings displayed two well defined phases of auxin induced gene transcription. Phase I (6 h) evidenced the selective dissociation of many RNA polymerase subspecies from the chromatin complex which was accompanied by the retention of three class II enzymes. Phase II occurred after 12 h of treatment when the dissociated enzymes including some species which were soluble in the 0 h controls became re-associated with chromatin. These induced RNA polymerases may be responsible for the synthesis of auxin induced RNAs. In contrast, the unresponsive 8 day hypocotyl did not display two phases of auxin induction. Phase one, the dissociation of the chromatin bound enzymes, occurred at 12 h (compared to 6 h for the 4 day seedling) and was not followed by the later translocation of any soluble enzymes towards the chromatin complex. The results support earlier findings suggesting that the developmental "phasing out" of RNA polymerase subspecies limits the hormone induced growth response of this tissue and thus is regarded as an off switch for the transcription of such hormone controlled gene sequences.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1978

Solubilization and developmental distribution of embryonic antigen of the chick red blood cell plasma membrane.

An antigen(s) on the surface of embryonic and newly hatched chick red blood cells was studied with antiserum absorbed with adult red blood cells. Because of the reappearance of the antigen or some cross-reactive antigen during myeloblastosis, attempts at solubilization and characterization of the antigen were pursued. Antigen was solubilized from whole red blood cell lysates or from red blood cell ghosts with 0.01 M Tris:0.1% Nonidet P40, pH 8.0. Antigen was assayed with an enhancement of agglutination assay. Enhancement apparently occurs because of available specific receptors for the antigen on newly hatched chick red blood cells. Antigen was also found to be present in plasma, and both the membrane-derived antigen and the plasma antigen were excluded from Sephadex G-100. Isoelectric focusing of the antigen extract indicated the presence of more than one molecular species with antigenic activity.

Age Factors↗
PubMed1978

A preliminary study of the superoxide dismutase content of some human tumors.

The cell cytosol superoxide dismutase (SODase) content of 46 human tumors was investigated. The extraction procedure of McCord and Fridovich was used with the epinephrine assay of Misra and Fridovich (J. Biol. Chem., 247; 3170-3175, 1975). The purpose of the study was to determine whether SODase could be reliably assayed from small, biopsy-sized pieces of tumor (0.5 to 1.0 g). In most cases it was possible to examined larger masses of tumor, which served as a control of the methodology. In this preliminary study SODase values, calculated from a standard curve derived from purified bovine blood SODase with a specific activity of 2584 units/mg, ranged from as little as 0.23 to as much as 160.5 units/g of tumor. These findings suggested that the procedures used might be feasable on a routine basis to determine the SODase content of tumors and its possible relationship to the radiation sensitivity of the tumors.

Breast Neoplasms↗
PubMed1977

Conditioned narcotic withdrawal in humans.

Subjective and physiological manifestations of the narcotic withdrawal syndrome were produced as a conditioned response. Withdrawal reactions precipitated by the narcotic antagonist naloxone in methadone-dependent volunteers were the unconditioned response. These data support clinical anecdotes of withdrawal symptoms occurring in former addicts when they return to their drug-related environment.

Adult↗
PubMed1975

Conditioning of narcotic abstinence symptoms in human subjects.

Clinical evidence suggests the possibility of conditioning of narcotic abstinence symptoms. Addicts report subjective and objective signs of withdrawal/craving when exposed to certain stimuli. This may partially explain the high rate of relapse to drug seeking behavior when treated addicts return to their home environment. Conditioning of narcotic abstinence symptoms was produced experimentally in five of eight volunteer subjects. Brief naloxone precipitated abstinence was the unconditioned response. The conditioned stimulus was a tone and odor. After an average of seven training trials, the tone and odor produced a conditioned abstinence response. The conditioned response consisted of subjective components (feelings of sickness, nausea, cramps, craving) and objective components (yawning, tearing, rhinorrhea, irregular respiration and transiently increased blood pressure). These laboratory findings support the anecdotal evidence regarding the existence of conditioned abstinence phenomena.

Acoustic Stimulation↗
PubMed1975

Tonic immobility in the blue crab (Callinectes sapidus, Rathbun) its relation to threat of predation.

The tonic immobility. response in the blue crab (Callinectes sapidus, Rathbun) was investigated in a series of seven experiments. Although reported to be a powerful variable in other species, preinduction electric shock produced inconsistent increases in the duration of tonic immobility with the blue crab; Manipulations that were more directly relevant to the fear of predation had considerably greater effects than shock. Physical damage to the chelipeds, mirror image stimulation, and immobilization beneath artificial glass eyes all produced significant prolongation of the immobility episode; Crabs immobilized on a bed of sand rather than on a hard surface showed shorter immobility durations, suggesting that opportunity for escape is an important variable affecting the immobility reactionmthe present results support the contention that threat of predation is the organizing principle behind tonic immobility

Animals↗
PubMedDate not supplied

Maternal serum human chorionic gonadotropin as a marker for the delivery of low-birth-weight infants in women with unexplained elevations in maternal serum alpha-fetoprotein.

We wished to ascertain whether the measurement of maternal serum human chorionic gonadotropin (MShCG) in the serum of pregnant women with unexplained elevations of maternal serum alpha-fetoprotein (MSAFP) would more precisely define those women at risk of adverse pregnancy outcomes. MShCG was measured in samples of serum obtained from women in the second trimester of pregnancy who had elevated MSAFP, normal Level II ultrasounds, and normal fetal karyotypes. Based on the characteristics of a receiver-operator curve for MShCG and birth weight, patients were divided into two groups and pregnancy outcomes were compared. Pregnant women with an unexplained elevation in MSAFP, who also had an abnormal MShCG (< or = 0.5 MoM > or = 2.5) were at significantly greater risk of delivering a low-birth-weight infant compared to women with a normal MShCG (43% and 15%, respectively; P = 0.013). They were also more likely to deliver a preterm infant (48% and 11.9%), respectively; P = 0.001). In the prediction of low birth weight, an abnormal MShCG had a sensitivity of 50%, a specificity of 81%, and a positive predictive value of 43%; in the detection of preterm delivery the values were 59%, 88%, and 48%, respectively. These findings suggest that in pregnant women with a second trimester unexplained elevation in MSAFP, abnormal MShCG levels may identify a group of women at high risk of preterm delivery or delivery of a low-birth-weight infant.

Adolescent↗
PubMedDate not supplied

Conditioning in human opiate addicts.

Eight volunteers maintained on daily methadone participated in a classical conditioning procedure to determine which if any of the elements of narcotic withdrawal could be conditioned; The unconditioned stimulus was the injection of a small dose of naloxone. The unconditioned response was a brief precipitated withdrawal syndrome. The conditioning stimulus was a tone, odor, and injection of saline. Conditioning was successful in the pilot study in 5 of 8 subjects. The conditioned response consisted of tearing, yawning, lacrimation, systolic blood pressure increase, respiratory irregularities and subjective feelings of narcotic withdrawal sickness (nausea, muscle aches, chills). A second group of 8 subjects showed, in addition to the above, evidence of conditioning of heart rate, respiratory rate, respiratory, rate and skin temperature decrease. These laboratory findings support the clinical reports of a conditioned withdrawal syndrome and suggest ways to improve treatment results by detecting and extinguishing or modifying conditioned responses.

Adult↗
PubMedDate not supplied

Expression of HOXD10 gene in normal endometrium and endometrial adenocarcinoma.

OBJECTIVE: Hox genes encode DNA transcription regulatory proteins that contain a conserved 61 amino acid protein called the homeodomain. Although best known for their role in cellular differentiation during embryonic development, aberrant expression of these genes has been associated with hematologic and solid neoplasms. The purpose of this study was to determine the relative expression of HOXD10 in human endometrial adenocarcinomas. METHODS: mRNA was isolated from 7 normal endometrial specimens and 28 endometrial adenocarcinoma specimens. cDNA was synthesized using random hexamer primers. The expression of HOXD10 relative to beta-tubulin (internal control) was assessed by densitometric comparison of co-amplified Phosphorus-32 (32P) labeled gene products separated by agarose gel electrophoresis. Direct sequencing of purified HOXD10 polymerase chain reaction product was also performed. RESULTS: The sequence of the purified HOXD10 product corresponds to the known DNA sequence reported in the National Institute of Health Gene Bank. mRNA expression of HOXD10 relative to beta-tubulin is significantly lower in endometrial carcinomas than in normal endometrium. Furthermore, the ratio of HOXD10 to beta-tubulin expression varies inversely with the histologic grade of the tumor (P = .0009). CONCLUSION: Cancer is a multistep process involving the aberrant expression of genes that regulate cell growth and differentiation. Human HOXD10 gene expression is altered in endometrial carcinoma and varies with the histologic grade of differentiation. This observation supports the theory that homeobox genes play a role in oncogenesis.

Adenocarcinoma↗