Specificity of short-loop feedback of luteinizing hormone in the rabbit.

The specificity of the gonadotropin short-loop feedback mechanism was investigated in castrated rabbits by blood sampling from an indwelling jugular venous catheter for follicle-stimulating hormone (FSH) after the intravenous administration of purified human luteinizing hormone (hLH). Although we have previously shown that such hLH administration results in a decrease of rabbit LH, no decrease in rabbit FSH was seen in these experiments. This specificity of LH feedback is compatible with the site of feedback being at the (1) pituitary level or (2) at the hypothalamic level provided two separate LH and FSH releasing factors exist.

Characterization of the poly(adenylic acid) sequences in RNA synthesized in vitro by mouse myeloma nuclei.

The size and quantity of poly(A)sequences made by mouse myeloma nuclei in vitro are dependent on the concentration of KCI, ATP, other ribonucleoside triphosphates, as well as the nature of the divalent cation in the reaction medium. Reduction of the KC1 concentration from 120 mM to 5 mM, for example, stimulates poly(A) synthesis 10- to 20-fold. These poly (A) sequences are similar in size to cellular nuclear poly(A), but the RNA molecules to which they are attached are much shorter than poly(A) containing RNA molecules made at 120 mM KC1.

Poly(uridylic acid) sequences in messenger ribonucleic acid of HeLa cells.

The poly(uridylic acid [poly(U)] sequences of 30 to 40 nucleotides found in the heterogeneous nuclear ribonucleic acid (RNA) Of HeLa cells are also present in the poly(adenylic acid) [poly(A)] containing messenger RNA (mRNA) of these cells. Twenty-five percent of the total poly(U) sequences in the cell are found in the cytoplasm after HeLa cells have been labeled for 2.5 h with 32P.

Preparation and properties of a poly A resin and its use in the isolation of naturally occurring poly U sequences.

A method for the covalent attachment of poly A, as well as other nucleic acids and nucleosides, to a methylene dianiline derivative of starch is described. The properties of this poly A resin and its use for the recovery of poly U sequences from both nuclear and cytoplasmic extracts of HeLa cells is described.

Short-loop feedback control of luteinizing hormone in the rabbit.

A radioimmunoassay for rabbit luteinizing hormone (rLH) in which rLH shows no significant cross-reaction with human LH (hLH) or human chorionic gonadotropin (HCG) was employed to test for the existence of a short-loop feedback for LH in the rabbit. Two weeks after castration, hCG and hLH were administered intravenously to rabbits, and the effects on circulating rLH were measured. Purified hLH (10 ng or 100 IU) produced significant depression of blood rLH within 30-60 min of intravenous injection.

Secretion of alpha subunits of luteinizing hormone (LH) by the anterior pituitary.

Free alpha subunit chains of the glycopeptide pituitary hormones have been found in the sera of normal subjects and postmenopausal women. To ascertain whether the alpha subunit of LH is directly secreted by the pituitary or formed as a result of degradation of intact LY in the periphery, alpha subunits and intact LH were measured by radioimmunoassay in human volunteers after LRF stimulation and purified LH infusion. In 4 subjects a loading dose of 90 IU, followed by the infusion of 22.

Secretion of alpha and beta subunits of TSH by the anterior pituitary.

We have attempted to determine whether blood concentrations of the alpha chains of TSH arise by direct pituitary secretion of alpha chain or by degradation of the intact hormone after secretion. Highly purified human TSH was administered by infusion to euthyroid volunteers; blood TSH concentrations were raised to 36 muu/ml. After TSH infusion, circulating blood alpha chain concentrations did not change.

Differential metabolism of large and small poly(A) sequences in the heterogeneous nuclear RNA of HeLa cells.

The heterogeneous RNA of the HeLa cell nucleus contains short internal poly(A) sequences which, in contrast to the longer poly(A) sequences at the 3' ends, are not found in messenger RNA of the cytoplasm. A distinct origin for each of these homologous sequences is evident when the effects of actinomycin D and 3'-deoxyadenosine on their biosynthesis are compared. The shorter poly(A) appears to be transcribed, while the longer one does not.

External irradiation of the hypophysis for Cushing's disease.

During the past 12 years 17 patients with Cushing's disease (bilateral adrenal hyperplasia secondary to excessive pituitary adrenocorticotrophic hormone) have been treated initially with external pituitary irradiation. Of the 15 patients who have had adequate follow-up, nine showed complete biochemical remission, and one showed biochemical improvement. There were no complications.