Isolating and sequencing the infrequent 3'-ends of a specific mRNA

Procedures are described for identification of very infrequent in vivo 3'-ends of RNA. After purification by filter hybridization, the 3'-ends were labeled with [5'-32P] cytosine-3'-P in the RNA ligase reaction. Significantly fewer counts were incorporated in the ligase reaction than in the polynucleotide kinase reaction to label 5'-ends. The incorporation was increased by increasing the RNA concentration 5-10 fold by using only one round of filter hybridization. Non-specific RNA binding could be eliminated by RNase A treatment of the filter if a great excess of denatured heterologous DNA was immobilized along with the DNA probe. Significant amounts of DNA were released when eluting the hybrid RNA from such filters. DNA inhibited the ligase reaction, while its DNase products were even more inhibitory. Treatment of the DNase products with alkaline phosphatase completely eliminated the inhibition. We detected no spurious 5'- or 3'-ends generated in the hybrid RNA by RNase A activity used to reduce the non-specific RNA. Also, RNase T1 could be used in place of RNase A to eliminate non-specific RNA binding, but about 25 times more RNase T1 (microgram/microgram) was needed. We used partial alkali digestion to sequence 3'-ends. A major (one hit) and minor (two hit) set of products were produced which could be distinguished from each other by alkaline phosphatase treatment and homochromatography of the products.

Intron/exon structure of the human gene for the muscle isozyme of glycogen phosphorylase

The intron/exon organization of the human gene for glycogen phosphorylase has been determined. The segments of the polypeptide chain that corresponds to the 19 exons of the gene are examined for relationships between the three-dimensional structure to the protein and gene structure. Only weak correlations are observed between domains of phosphorylase and exons. The nucleotide binding domains that are found in phosphorylase and other glycolytic enzymes are examined for relationships between exons of the genes and structures of the domains. When mapped to the three-dimensional structures, the intron/exon boundaries are shown to be widely distributed in this family of protein domains.

Purification and crystallization of bovine liver phosphorylase

We have purified and crystallized bovine liver phosphorylase a. Starting from 2.5 kg of liver, we obtain 250 mg of phosphorylase a, with a specific activity of 90 units/mg, representing 15% recovery. SDS polyacrylamide gels show three bands, a 95 kDa band with the same mobility as muscle phosphorylase, and two smaller bands of 55 kDa and 40 kDa, which are probably proteolytic fragments. These fragments remain associated and have native conformation and catalytic activity. Crystals which diffract to 2.8 A resolution, were prepared by the hanging drop method using polyethylene glycol PEG 4000 as precipitant. The crystals were prepared in the presence of activators maltotriose and phosphite and crack when placed in solutions containing the inhibitors glucose and caffeine. This suggests phosphorylase is present in an active conformation.

HPLC determination of benzthiazide in biologic material

An assay was developed for benzthiazide in plasma, urine and feces, using high performance liquid chromatography (HPLC). A reverse-phase column was employed, with quantitation af 280 nm, using polythiazide as an internal standard. In three of four human subjects who received a 50 mg benzthiazide tablet the plasma concentrations were below the 10 ng ml-1 sensitivity limit of the assay, and the urinary recovery averaged less than one per cent of the dose. One subject received a 50 mg dose as both a tablet and a solution; the urinary recoveries for these two doses were 1.7 and 10.4 per cent, respectively. Fecal samples, obtained from two subjects who received 50 mg tablets, were estimated to contain approximately 80 per cent of the administered dose.

Characterization of natriuretic activity from posterior pituitary lobes

Previous studies have indicated the existence of natriuretic factors of hormonal nature with the posterior pituitary gland as a possible site of origin. It was in this light that a series of experiments was designed to examine the posterior pituitary for such factors. Acetic acid extracts of porcine and bovine posterior pituitary lobe tissue were subjected to gel filtration on Sephadex G-25. Several fractions in the molecular size range of 1000 were obtained which possessed potent natriuretic activity as assayed in rats. The activity of these fractions maximally increased sodium excretion to 6-8 muequiv./min, a 10- to 40-fold increase above control, when administered intraperitoneally to hydropenic, conscious rats. However, oxytocin and vasopressin, present in the posterior pituitary are natriuretic. These hormones were measured by radioimmunoassay, and invariably only those fractions which contained vasopressin and (or) oxytocin possessed natriuretic activity. Moreover, the extent of the natriuresis could be accounted for by the vasopressin and (or) oxytocin content of the test fractions. The natriuretic property of this material was abolished by treatment with thioglycollate. Further purification of natriuretic fractions by ion exchange resins, thin-layer chromatography and isoelectric focusing failed to resolve natriuretic activity from vasopressin and oxytocin. Similar results were observed following analysis of fractions isolated by gel filtration of acetic acid extracts of ventral hypothalamus tissue. The natriuretic fractions isolated from hypothalamic tissue were indistinguishable from oxytocin and vasopressin. These experiments suggest that the natriuretic activity in neurohypophyseal extracts can be attributed to oxytocin and vasopressin.

Human and monkey prolactin and growth hormone: separation of polymorphic forms by isoelectric focusing

The feasibility of using isoelectric focusing for the separation of primate pituitary growth hormone from prolactin and for the characterization of polymorphic forms of these hormones was explored. In a pH 3--10 gradient, extracts of both human and cynomolgus monkey pituitaries were each resolved into 4 growth hormone components and at least 3 prolactin components, as shown by radioimmunoassay. In narrower gradients (of 2--3 pH units) greater resolution was achieved; the principal growth hormone components were well separated from the principal prolactin components but there was overlapping of some minor components. A partially purified human prolactin preparation was found to contain 4 prolactin components, one of which had a prolactin/growth hormone ratio of 760. Clinical grade human growth hormone was also resolved into at least 5 prolactin and 5 growth hormone components, many of which had higher pI values than those found in pituitary extract. Under the conditions used, both growth hormone and prolactin were found to be polymorphic with respect to isoelectric point. Some of the human prolactin components were found to contain less than 0.2% growth hormone by radioimmunoassay. Monkey growth hormone containing 0.01% prolactin was isolated. These findings demonstrate that isoelectric focusing is useful for the preparation of both growth hormone and prolactin which are essentially free of one another. Furthermore, the polymorphic forms were repeatedly found in preparations obtained by several methods and from 2 different species, suggesting that these forms are not artifacts.

Functional evaluation of prolactin secretion: a guide to therapy

Stimulation and inhibition tests are proposed for evaluating prolactin secretion. Thyrotropin-releasing hormone (TRH) stimulates the release of prolactin from the pituitary. Chlorpromazine acts presumably at the hypothalamic level to increase prolactin secretion. L-Dopa (D,L-alpha-hydrazino-alpha-methyl-beta-[3,4-di-hydroxyphenyl]) has the opposite effect; it inhibits prolactin secretion and may be effective in suppressing galactorrhea.

A radioimmunoassay for human prolactin

A radioimmunoassay for primate prolactin has been developed, with [(131)I] monkey prolactin, and antibodies to monkey or human prolactin. The assay is specific for prolactin; human growth hormone, and human and monkey placental lactogen show no significant crossreaction. The assay is sensitive enough to measure prolactin concentrations in the sera of most humans studied. The concentration of prolactin in the serum of normal children and adults of either sex was usually below 30 ng/ml, while very high concentrations (up to 500 ng/ml) were observed in newborn infants. The serum prolactin concentration during the menstrual cycle showed no definite increase in the luteal phase. Of 24 patients with galactorrhea, 20 had prolactin concentrations above 30 ng/ml; the highest value observed was 1500 ng/ml. In contrast, 12 of 13 patients with acromegaly had concentrations within the normal range. During pregnancy, the concentration of prolactin in serum rose progressively from an average of 30 ng/ml in the first trimester to 200 ng/ml at term. Postpartum, prolactin concentrations fell to normal levels after 1-2 weeks. Suckling was a potent stimulus to prolactin release, increasing its concentration in serum some 10- to 20-fold.