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Biomedical subjects

D C Johnson

Publications and source records attributed to D C Johnson.

At least 235 records · Page 13Linked to original sources
PubMed1979

Maintenance of functional corpora lutea in androgenized female rats treated with OMSG.

Rats were androgenized by injection of 50 micrograms testosterone propionate on the 5th day after birth and when adult were treated with 5 i.u. PMSG; some of the animals were mated. Serum was obtained daily and the concentrations of progesterone, 20 alpha-dihydroprogesterone and prolactin, estimated by radioimmunoassays, were compared to values found for mated, but not ovulating, androgenized females and those for normal pregnant females. Ovulation and luteinization of follicles occurred. The concentration of progesterone increased after the injection of PMSG and remained elevated for at least 10 days; mating did not alter the progesterone levels. The concentration of 20 alpha-dihydroprogesterone was also elevated but the ratio of the level of progesterone to this steroid was generally greater than unity. Prolatin levels were elevated in the rats which ovulated. It is concluded that the corpora lutea induced in androgenized females by PMSG are functional and maintained.

20-alpha-Dihydroprogesterone↗
PubMed1978

Effect of adrenalectomy on temporal patterns of serum gonadotropin levels.

To determine whether adrenocortical function influences rhythmic gonadotropin patterns in male rats, blood samples were obtained by rapid decapitation from control and adrenalectomized male rats at 3-h intervals over a 24-h period (14 h light/day, 4 a.m.--6 p.m.). Control animals showed periodicity in serum LH, prolactin (Prl) and corticosterone similar to that reported previously. Peak and trough serum levels of corticosterone and Prl occurred at 5 p.m. and 8 a.m. respectively whereas those for LH occurred at 11 p.m. and 11 a.m. Serum FSH levels did not vary with circadian periodicity. 15 days after adrenalectomy, serum LH levels continued to fluctuate with a circadian periodicity but showed a marked phase shift; peak LH levels were observed at 8 a.m. The absence of adrenal hormones did not result in altered FSH levels nor was the phase of the Prl rhythm significantly altered.

Adrenal Cortex↗
PubMed1978

Evaluation of a glassy-carbon electrode for amperometric detection of selected methylxanthines in serum after their separation by reversed-phase chromatography.

We examined the relative merits of direct-current, pulse, and differential pulse amperometry at a flow-through, glassy-carbon electrode used in monitoring column chromatography. We give a rapid, simple procedure for determining theophylline (1,3-dimethylxanthine) in 20--100 microliter of blood serum. Interference by 1,7-dimethylxanthine, a metabolite of caffeine, is compared for photometric and amperometric detection, and some advantages of combined photometric and amperometric detection are discussed.

Chromatography, Liquid↗
PubMed1977

MEDINFO--a medical information system.

The MEDINFO (MEDical INFOrmation) system is a general purpose computer-based information storage, retrieval, and analysis system. It is designed for a time sharing, on-line computer system for the rapid and easy creation, maintenance, and analysis of general data files. A wide variety of types of information may be used. These include numeric, categoric, text, date, and multiple-response. The file structure allows several sets of data, including date-orientated data, to be used. MEDINFO permits a study to be created, a description of the data made, data to be entered and updated into records, and for the data to be displayed or analyzed by the investigator without programmer intervention.

Computers↗
PubMed1977

Evidence for macromolecular synthesis in stimulation of the estrogen synthesizing system of the immature rat ovary by PMS.

Exposure of immature rat ovaries to pregnant mare's serum gonadotropin (PMS) results in a prompt increase in testosterone and progesterone output but synthesis of estradiol (E2) increases only after a lag period of several hours. Actinomycin D (Act-D) given with PMS did not inhibit testosterone or progesterone production but the estrogenic response was prevented. Delay in administration of the Act-D until 12 hr after PMS resulted in a transient increase in E2 secretion lasting less than 12 hrs. When Act-D was given 12, 16 or 20 hrs after PMS, and ovarian steroid production measured by a one hr incubation, no inhibition of progesterone, testosterone or E2 was found; the synthesis of the latter two steroids was increased by the drug. Cycloheximide, on the other hand, was most effective at inhibiting testosterone and E2 production when it was given at 12 hrs; the drug was progressively less effective in lowering production of these steroids when it was given at 16 or 20 hrs. Cycloheximide did not alter progesterone production unless it was given at the same time as PMS. The results are consistent with the view that the induction of the estrogen synthesizing system of the immature rat ovary by gonadotropin involves, during the first 12 hrs, production of a material sensitive to Act-D inhibition (mRNA?) and then production of a material sensitive to cycloheximide inhibition (protein-enzymes?). The continued production of both of these materials appears to require the continual presence of gonadotropin.

Animals↗
PubMed1977

Low thoracic duct ligation for postoperative chylous effusions in infants and children.

Three patients aged from three months to six years underwent thoracic duct ligation at the level of the diaphragm for chylothorax which occurred following cardiac operations. Another three-month-old patient underwent thoracic duct ligation for massive postoperative chylopericardium. Indications for operation were a large recurrent chyle accumulation or prolonged chyle drainage. Operative ductograms to deliniate the cisterna chyli and to exclude the presence of multiple lymph channels were performed in three patients. Excellent postoperative results were obtained in all patients for periods of up to two years. Low thoracic dust ligation is a reliable means of control of postoperative chylothorax and lengthy persistence with conservative treatment is no longer necessary.

Child↗
PubMed1977

Response of the pituitary-testicular axis to luteinizing hormone-releasing hormone in the immature male rat.

Follicle stimulating hormone (FSH), luteinizing hormone (LH), testosterone and androstenedione were measured by radioimmunoassays in the sera of immature male rats treated with luteinizing hormone-releasing hormone (LH-RH). A single dose of 10, 20, 40 or 80 ng of LH-RH produced a prompt increase in serum LH: signfiicant changes in FSH were found only with the two larger doses. Serum testosterone increased to peak levels in 20 to 40 min and returned to control level by 120 min. Changes in androstenedione were temporally similar but smaller in magnitude. Four doses of 20 or 40 ng LH-RH given at 20 min intervals did not increase serum LH or testosterone concentrations above those found with a single injection; FSH was slightly higher after the fourth dose. However, 40 ng LH-RH given every 20 min for 2 h produced a dramatic increase in serum LH and FSH: serum and testicular androgens were also much higher during the second hour. A 2 h stimulation with 80 ng LH-RH given ip at 30 min intervals did not alter the response to the same treatment given 24 h later; i.e., neither the pituitary nor the gonad was primed by previous exposure to increased levels of LH-RH or gonadotrophins. These results suggest that a single pulse of LH-RH produces a predictable response in the animal, but multiple episodic stimuli produce variable responses: testes, on the other hand, produce androgens as long as gonadotrophins are available.

Androstenedione↗
PubMed1977

Temporal changes in ovarian ornithine decarboxylase and cyclic AMP in immature rats stimulated by exogenous or endogenous gonadotrophins.

Pregnant mare serum gonadotrophin given intravenously to immature rats caused a maximal (x 70) increase in ornithine decarboxylase activity (ODC) at 3 h; enzyme activity declined to about ten times the control levels by 9 h and a second rise began after about 20 h. Anti-PMSG given 30 min after PMSG reduced the peak response by 70%. Actinomycin D, or cycloheximide, completely prevented an increase in ODC when given with PMSG, but only cycloheximide lowered the enzyme activity when given 18 h later. Ovine FSH plus LH also produced a peak in ODC at 3 h but the activity decreased quickly and by 9 h it was at the control level. Secretion of endogenous FSH and LH, induced by hourly injections of LH releasing hormone (LH-RH) increased ODC to the same extent as did the exogenous hormones; ODC was still higher than in the controls 4 h after the last dose of LH-RH. Increased endogenous levels of FSH and LH did not consistently raise ovarian cyclic AMP content and the increases found were much less than those obtained after injection of PMSG or FSH+LH. The results indicate that increased ODC is induced and maintained by the continual presence of gonadotrophin. The dependence of increased ODC upon increased cyclic AMP cannot be unequivocally determined because of important differences in the timing of the responses and the difficulty in determining biologically significant changes in cyclic AMP.

Age Factors↗
PubMed1976

Angiographic assessment of anomalous origin of the left coronary from the pulmonary artery in infancy and childhood.

Angiographic findings in five paediatric patients with anomalous left coronary artery arising from the pulmonary artery are presented. An attempt is made to provide an angiographic rationale of some aspects of the pathophysiology and electrocardiography in this condition, and the vital importance of angiography in selecting the appropriate surgical approach is underlined.

Angiocardiography↗
PubMed1976

Proestrous gonadotropin levels in thyroparathyroidectomized female rats.

Intact and TPTx animals showed the expected afternoon increase in serum LH,FSH and prolactin levels. But the afternoon increase in serum LH levels in TPTx rats was less than that observed for intact animals (p less than 0.001). Neither serum prolactin nor FSH levels were altered by TPTx.

Animals↗
PubMed1976

Stimulation of the estrogen synthesizing system of the immature rat ovary by exogenous and endogenous gonadotropins.

Immature rat ovaries increase their secretion of estradiol (E2) when stimulated by gonadotropins but only after a lag period of several hours. Once established, estrogen secretion can be maintained, or increased, by the continued presence of gonadotropin. A combination of ovine FSH+LH given at 2 hr intervals stimulated the estrogen synthesizing system (ESS) of the ovary and serum E2 showed a pronounced rise between 16 and 20 hrs after the initial injection. When given every 2 hrs for 5 doses (0-8 hrs) serum E2 was undetectable. However, it was increased if 20 IU PMS was injected at the time of the last dose of FSH+LH. Endogenous FSH+LH, increased by hourly injections of LH-releasing hormone for a period of 8 hrs, stimulated the ESS: serum E2 increased at the expected when this treatment was followed by an injection of PMS. Anti-PMS antiserum given 12 hrs after PMS, prevented the expected rise in serum E2 at 24 hrs. However, FSH, LH or a combination of the two given every 2 hrs beginning at the time of the anti-PMS produced an increase in E2 secretion; the combination was more effective than either hormone alone. These results are consistent with the interpretation that a combined FSH-LH action is responsible for induction fo the ESS in the immature rat ovary. The combination of homones is also very effective in maintaining estrogen secretion but some function appears possible with FSH or LH alone.

Animals↗
PubMed1976

Stress-induced gonadotropin and prolactin secretory patterns.

To further evaluate the influence that sex, time of day and/or stage of the estrous cycle have on stress-induced changes in gonadotropin secretory patterns, rats were subjected to acute ether stress and subsequently sacrificed at 1.5, 3, 5, 10 and 15-min intervals. A significant change in FSH levels was not detectable, however serum LH levels consistently showed a transient elevation, and prolactin release occurred rapidly and in large increments in every case. Variation in basal hormone levels due to sex, circadian rhythmicity, or estrous cyclicity did not alter the pattern of the response of individual hormones to the stress but did markedly influence the magnitude of the response.

Animals↗
PubMed1976

The response of the immature rat ovary to gonadotrophins: acute changes in cyclic AMP, progesteron, testosteron, androstenedione and oestradiol after treatment with PMS or FSH + LH.

Radioimmunoassays were used to measure changes in progesterone, testosterone, androstenedione, oestradiol, gonadotrophin and ovarian cyclic AMP in immature female rats during the first 24 h after exposure to slowly (PMS) or rapidly (FSH + LH) disappearing gonadotrophins. Cyclic AMP was increased 30 min after injection of either kind of gonadotrophin but it had returned to control level within 4 h. Serum and ovarian testosterone and androstenedione also increased to a peak at 30 min but decreased to base line by the 4th h. Multiple injections of FSH + LH maintained an elevated serum testosterone level but they had little effect upon the secretion of androstenedione. Serum and ovarian progesterone increased quickly after treatment with gonadotrophin. With PMS the peak in the serum was reached at 8 h, it remained high for 4 h and then fell precipitously between the 12th and 16th h. FSH + LH produced a prompt increase in serum progesterone but the level could be maintained only by repeated doses given every 4 h. Oestradiol was not increased in the serum or the ovot produce an increase in oestrogen but a transient increase was found with 3 doses; 4 doses kept an elevated level of oestradiol for 12 h. These results indicate that the aromatizing system of the immature rat ovary is relatively inactive and that continual stimulation by gonadotrophin for about 10-12 h is necessary to bring about increased function. In contrast, the mechanisms for the synthesis and secretion of progesterone and androgens are vary active and can be immediately stimulated by exposure to gonadotrophins.

Androstenedione↗