Distribution of luteinizing hormone releasing hormone in the canine hypothalamus: effect of castration and exogenous gonadal steroids

The effect of exogenous gonadal steroids or orchidectomy on the distribution and concentration of luteinizing hormone-releasing hormone (LHRH) in the hypothalamus of the dog was studied. Various hypothalamic area of the canine brain were extracted with 90% methanol and processed, and LHRH was assayed, using a specific radioimmunoassay. The highest concentration of immunoreactive LHRH was found in the infundibular, premammillary, preoptic, and suprachiasmatic areas in intact dogs. Measurable amounts of LHRH were found in the mammillary and lateral hypothalamic regions. The hypothalamus in the male dog had significantly (P < 0.05) higher LHRH concentrations 3 mm lateral to the midsagittal line (the lateral hypothalamic area) as compared with the area in the anestrous female dog. Daily estrogen treatment of female dogs with 0.2 mg/day or 1 mg/day, IM, or with testosterone propionate (1 mg/day, IM) for 3 weeks increased LHRH concentration 2.5- to 5-fold in the mammillary, premammillary, and infundibular areas and almost 40-fold in the preoptic, rostral commissural area and in the lateral and dorsal hypothalamic regions. Orchidectomy caused an increase in LHRH concentration in the preoptic and suprachiasmatic area with a concurrent decrease in LHRH in the infundibular area. Therefore, in the dog, LHRH is possibly synthesized or transported (or both) from different regions of the hypothalamus to the median eminence, and the gonadal steroid feedback mechanism is complex, involving multiple sites of action in the hypothalamus and the components of the limbic system.

Measurement of serum C-peptide immunoreactivity by radioimmunoassay in insulin-dependent diabetics

A radioimmunoassay for C-peptide utilizing synthetic C-peptide as an antigen and tyrosylated synthetic C-peptide for iodination was evaluated for its clinical use. Mean fasting C-peptide levels in 24 normal subjects was 2.6 +/- 0.8 ng/ml. During the oral glucose tolerance test, baseline C-peptide in five normal subjects was 1.5 +/- 0.8 ng/ml, and at 60 min was 5.6 +/- 1.6 ng/ml. For two insulin-dependent diabetic patients, diagnoses of factitious hypoglycemia were documented on the basis of simultaneous free insulin and C-peptide determinations. Sera from 24 insulin-dependent diabetics were analyzed for free and total immunoreactive C-peptide and insulin levels. For 20% of juvenile and 64% of maturity-onset diabetics, the presence of proinsulin-like material bound to insulin antibodies was demonstrated by measurement in unextracted serum. This accounted for 20% to 100% of total C-peptide immunoreactivity in these patients. Simple polyethylene glycol precipitation of immune complexes and the measurement of free immunoreactive C-peptide in the supernatant demonstrated subnormal levels (less than 0.5 ng/ml) in all juvenile diabetics and normal levels (1.8 +/- 1.3 ng/ml) in 70% of maturity-onset diabetics.

Isolation and partial characterization of prolactin from equine pituitary gland (hypophysis)

Highly purified equine prolactin was prepared from equine pituitary glands (hypophysis) by serial extractions with water at pH 5.5, 0.1 M (NH4)2SO4 at pH 4.0, and 0.25 M (NH4)2SO4 at pH 5.5 to remove other hormones, and then finally with 70% ethanol at pH 9.3 to 10.0 to extract prolactin. Preliminary purification of the extract involved salting out other substances with 0.1% NaCl at pH 9.0. Prolactin was precipitated out by adding three times the volume of 95% ethanol at 4 C. This prolactin preparation had a biological potency of 24 IU/mg. Further purification by isoelectric focusing on a pH gradient of 5 to 7 gave three prolactin components with the following characteristics: isoelectric point 5.8, 5.7, and 5.25; biological potencies (IU/mg) 35.6, 19.6, and 11.3. The major component had a molecular weight of 25,000, an isoelectric point of 5.8, and a biological potency of 35.6 IU/mg. Antiserum produced against this component did not cross-react with equine follicular stimulating hormone, luteinizing hormone, and growth hormone, but did cross-react with ovine and bovine prolactin. Human and murine prolactin had little cross-reactivity with the equine prolactin antiserum.

Enhancing effect of thyroxine on tumor growth and metastases in syngeneic mouse tumor systems

We studied the effect of thyroxine treatment on tumor growth and metastases resulting from tumor implants on the hind feet of mice in two syngeneic systems. In control, untreated A/Jax mice, tumor Sarcoma 1 at Day 14 after implantation had average tumor weight of 582 +/- 60 (S.D.) mg and showed an incidence of 57% metastases to regional popliteal nodes and 5% metastases to thymus. In contrast, the thyroxine-treated group (40 microgram/mouse s.c., 5 times/week for 1 month) had an average tumor weight of 808 +/- 56 mg (p less than 0.001), and metastases to popliteal nodes and thymus were 90 and 35%, respectively. In another syngeneic tumor system, Lewis fibrosarcoma was implanted in C57BL/6J mice, and the tumor weight and metastatic index (derived from the number and size of the pulmonary tumor foci) were determined at Day 28. Again, the synthetic L-thyroxine treated group showed a significant enhancement tumor growth and metastatic index. The mean tumor weight in the treated group was 385 +/- 26 mg (control, 694 +/- 25 mg; p less than 0.005) and metastatic index was 84 +/- 29 (control, 30 +/- 25; p less than 0.001). Induced hypothyroidism (treatment with 131I, 100 microCi/mouse i.p.) showed the reverse effect on both tumor systems. These results suggest that both tumor systems are dependent on thyroid hormones for their growth and spread.

Improved indirect and direct radioimmunoassay for carcinoembryonic antigen

Values obtained by the indirect and the direct assays for carcinoembryonic antigen by use of the "CEA Roche" method and reagents differ significantly. In 32 samples the latter method gave values almost twofold those obtained by the former. The mean ratio for direct/indirect was 1.9 +/- 0.6. Analytical recovery experiments on samples to which known amounts of the antigen had been added showed a similar disparity. A simple modification of these two procedures, involving addition of normal human plasma (containing less than 2.0 microgram of the antigen per liter) to standards, eliminated this discrepancy. In the indirect method, standards were added to normal human plasma, then extracted with perchloric acid before assay. In the direct assay normal human plasma instead of goat serum, was added to standards. With these modifications the analytical recoveries of added CEA by the indirect and direct methods were 87 +/- 17% and 99.7 +/- 8%, respectively, and the mean ratio between two methods was 1.2 +/- 0.4.

Improved indirect and direct radioimmunoassay for carcinoembryonic antigen

Values obtained by the indirect and the direct assays for carcinoembryonic antigen by use of the "CEA Roche" method and reagents differ significantly. In 32 samples the latter method gave values almost twofold those obtained by the former. The mean ratio for direct/indirect was 1.9 +/- 0.6. Analytical recovery experiments on samples to which known amounts of the antigen had been added showed a similar disparity. A simple modification of these two procedures, involving addition of normal human plasma (containing less than 2.0 microgram of the antigen per liter) to standards, eliminated this discrepancy. In the indirect method, standards were added to normal human plasma, then extracted with perchloric acid before assay. In the direct assay normal human plasma instead of goat serum, was added to standards. With these modifications the analytical recoveries of added CEA by the indirect and direct methods were 87 +/- 17% and 99.7 +/- 8%, respectively, and the mean ratio between two methods was 1.2 +/- 0.4.

Observations on the ovaries of zebu cattle in Northern Nigeria

A morphological study was carried out on ovaries of 236 local zebu cattle. Ovaries from 189 of the cattle were found to be abnormal grossly. Histological observations indicated changes due to old age. The findings are discussed in relation to the occurrence of low reproductive efficiency in cattle in Northern Nigeria.

Serum hydrocortisone (cortisol) values in normal and adrenopathic dogs as determined by radioimmunoassay

Using a specific radioimmunoassay, serum hydrocortisone values were measured in dogs. Between 9:00 AM and 10:00 AM, the base-line hydrocortisone value for 56 clinically normal dogs ranged from 6.0 to 28.5 ng/ml, with a mean value of 17.8 +/- 1.32 ng/ml (mean +/- SEM). Marked differences due to age, sex, body weight, or breed were not observed in the hydrocortisone values. In 11 dogs with definitive hyperadrenocorticism, serum hydrocortisone values were from 32 to 148 ng/ml. In 2 dogs with hyperadrenocorticism, the values were 4.5 and 3.1 ng/ml. The estimation of serum hydrocortisone values by radioimmunoassay is simple and precise, and can be utilized to aid in the diagnosis of adrenopathy in dogs.

The relationship of thyroid-stimulating hormone (TSH), thyroxine (T4), and triiodothyronine (T3) in primary thyroid failure

Thyroid-stimulating hormone (TSH), serum thyroxine (T4) and triiodothyronine (T3) in sera of 100 patients with primary thyroid failure were measured by radioimmunoassay. Effective thyroxine ratio (ETR) was also measured in 69 of these sera. TSH was elevated in all, with a mean of 76.7 +/- 55 micromicron/ml (range 11 to 140 micromicron/ml, and was used to confirm the diagnosis. Mean T4 and T3 levels in the group were 1.8 +/- 1.5 microgram/100 ml (range less than 0.2 to 7.0 microgram/100 u.) and 76.7 +/- 76 ng/100 ml (range less than 10 to 600 ng/100 ml), respectively. Mean ETR was 0.81 +/- 0.05. A moderate inverse relationship was observed between TSH and T4 (r = 0.73), in contrast to TSH and T3 and TSH and ETR, which showed comparatively poor relationships (r = 0.41 and 0.43). This observation, in addition to the finding that 17 patients had subnormal T4 but normal or elevated T3, suggests that normal T3 levels alone may not be sufficient to maintain euthyroidism. In contrast, there were only three clinically hypothyroid patients who had elevated TSH, normal T4, but subnormal T3 levels. This study indicates that T4 and T3 may function together to maintain euthyroidism, and that in addition to serum TSH, T4 determination has more diagnostic value than serum T3 or ETR in these patients.

Possible source and control of trauma-induced glucagonemia in dogs

Plasma concentrations of glucose, insulin, and glucagon were studied in 10 adult mongrel dogs given (intravenous administration) a large dose of glucose (1g/kg of body weight) both before and after partial (50%) pancreatectomy. A proportional decrease in plasma immunoreactive insulin was observed in partial pancreatectomized dogs. Peak insulin response decreased from presurgery concentrations of 71 +/- 14 muU/ml (mean +/- standard error of the mean) in the dogs before surgical operation (presurgical value) to 52 +/- 6 muU/ml 1 or 4 days after surgical operation. Partial pancreatectomized dogs also showed a reduced plasma glucose removal rate. Fasting plasma concentrations of glucagon, on the other hand, increased by about 80%, from 253 +/- 25 pg/ml to 460 +/- 43 pg/ml 24 hours after operation. Despite an increased glucagon concentration in the dogs after partial pancreatectomy, plasma concentrations of glucagon responded (decreased) to large gulcose dosage administration. Plasma glucagon concentration returned to presurgical value by the 4th postsurgical day.

Radioimmunoassay for serum cortisol with 125I-labeled ligand: comparison of three methods

We evaluated a previously modified double-antibody radioimmunoassay for serum cortisol. It was compared with the conventional double-antibody method that includes the usual extraction step, and also with an antibody-coated tube method. In this modified method, cortisol was released from its binding globulin by enzymatic degradation rather than by extraction with ether, and a preincubated mixture of first and second antibody was used to separate antibody-bound cortisol from free. These two steps shortened total asssay time significantly. Results still correlated well (r = 0.87) with results by the conventional melthod, but the antibody-coated tube method gave lower results (r = 0.61). Because of its good correlation with the conventional method, this method was thought to be more accurate. In 52 normal subjects, mean cortisol concentrations at 0800 and 1700 hours were 161 +/- 52 (SD) mug/liter and 91 +/- 27 mug/liter, respectively. In 16 normal subjects, cortisol values before and after dexamethasone treatment (1 mg at midnight) were 134 +/- 53 mug/liter and less than 20 mug/liter. In the same subjects, cortisol concentrations before and 30 min and 60 min after Cortrosyn (synthetic corticotropin1-24, 0.25 mg) administration were 103 +/- 25, 205 +/- 45 and 223 +/- 51 mug/liter, respectively.

An improved radioimmunoassay of serum gastrin using commercial kit

Our experience with a commercially available kit for the measurement of serum gastrin has been reported. Significant non-specific interference was noted by the addition of serum contents in the assay which lead to erroneous results. Use of gastrin free serum as a diluent in the standard curve was found to improve the mean recovery of added gastrin. With this modification the procedure was evaluated for its clinical application. In 30 normal subjects, the fasting mean gastrin level was 78.7 plus or minus 31.9 (S.D.) pg/ml; in 18 of these individuals the postprandial mean level was 118.3 plus or minus 26.7 (S.D.) pg/ml. In 15 patients with pernicious anemia the mean level was 912 plus or minus 779 pg/ml; and in 4 patients with Zollinger-Ellison (ZE) syndrome the mean gastrin level was 1950 plus or minus 379 (S.D.) pg/ml. A significant rise in gastrin level was noted in patients with kidney failure during and after dialysis (p smaller than 0.05).