Tar photoxicity and phototherapy for psoriasis

The photoxicity of coal tars was determined by comparing the ultraviolet light (UVL) energy required to produce erythema at tar treated sites (minimal phototoxic dose [MPD]) with the energy required to produce the same degree of erythema at untreated control sites (minimal erythema dose [MED]). The ratio of MED/MPD is the photoxic index (PI). Tars that were phototoxic had a PI of greater than 1. Using a UVA (320 to 400 nm) and a tuvb (290 to 320 nm) light source, 15 subjects and six tars were tested. All tars were phototoxic to UVA but not to UVB (P smaller than 0.0001). Although tar and UVL is a widely accepted treatment for psoriasis (Goeckerman therapy), the light sources employed at normal exposure times provide insufficient UVA energy to produce a phototoxic reaction to the tars are used. The therapeutic response seen in psoriatic patients treated with tar and UVL should therefore not be attributed to tar phototoxicity.

Effect of relaxin on mammary gland growth and lactation in the rat

Mammary DNA, RNA and RNA/DNA were measured in groups of 10 ovariectomized rats treated for 20 days with relaxin (R) in doses of 20 and 90 guinea pig units (GPU) alone or in combination with 1 mug estradiol benzoate (EB) or EB plus 3 mg progsterone (P). No treatment, EB only, and EB plus P served as control groups. Twenty GPU R alone significantly increased DNA over the no treatment group while 90 GPU did not increase DNA any higher. Although DNA values for the EB group were higher than no treatment and EB plus P higher than EB, R was not effective in increasing DNA in combination with either EB or EB plus P.R alone at either level did not change RNA from the no treatment group, but 90 GPU R in association with EB and both levels of R in association with EB plus P significantly reduced RNA in relation to the approiate control groups. Relaxin acts synergistically with estrogen and progesterone to develop the mammary apparatus and at the same time to suppress lactation. Removing the inhibitory effects of relaxin at parturition may be an important prelude to lactogenesis.

Mammary gland growth in the hypophysectomized pregnant rat (38522)

Sprague-Dawley-Rolfsmeyer rats were hypophysectomized on days 11, 12 or 15 of pregnancy and sacrificed on day 20 to determine the extent of mammary development, as assessed by determination of nucleic acid content. The DNA of six abdominal-inguinal glands in the hypophysectomized groups was not significantly different from that in the sham-operated pregnant or intact pregnant control groups. All groups maintaining pregnancy had significantly higher DNA contents in mammary glands than virgin control or hypophysectomized aborted groups. In order to determine the minimal numbers of placental-fetal units required to maintain pregnancy and mammary gland growth, fetuses and placentas were removed on day 12 of pregnancy in addition to the pituitary so that only one fetus and one placenta remained in the uterus of a group of 6 rats with other groups having 2, 3, 4, 5 remaining. Pregnancy was maintained with only one placental-fetal unit, but mammary gland proliferation was significantly lower than the control group on day 20 of pregnancy. Three to five conceptuses supported mammary proliferation during the latter half of pregnancy at a level not significantly different from intact or sham-operated control groups. Removal of placental units on day 12 in rats having pituitaries intact resulted in no mammary DNA change when 1-5 units remained. Removal of pitutaries on day 12 and placental-fetal units on day 14 also resulted in no change in mammary DNA with as little as two placentas (minus all fetuses),while only one placenta remaining resulted in a significantly lower mammary DNA than in groups wtih 2 or more placentas.

Thyroxine-induced hyperthyroidism upon the reproductive performance of female rats

L-Thyroxine (L-T4) was injected into mature rats daily at levels of 0, 3, 6, 12, 24, 48 and 96 mug/100 g body weight through estrous cycling, conception, pregnancy, parturition and 20 days of lactation. Mothers which lactated to 20 days were killed and mammary glands measured for DNA and RNA content. Those which were not able to maintain their pups were killed on the day when all pups died. Estrous cycling and pregnancy were not markedly effected by exogenous L-T4 at levels 3-96 times the normal thyroxine secretion rate in rats. After parturition the mothers on L-T4 above 12 mug did not allow the pups to suckle. As a result the pups died within 2-7 days after birth. Levels of L-T4 from 3 to 12 mug allowed lactation to progress, but survival of pups to day 20 of lactation was significantly lower than in the normal control group. The results of this study indicate that high levels of L-T4 inhibit mammary growth and mild secretion. This, in turn, results in the loss of pups, probably through depletion of prolactin as a result of higher metabolic rate due to hyperthyroidism.

Thyroidal content of thyrocalcitonin in lactating rats

Thyrocalcitonin (TCT) content of thyroid glands was determined by bioassay in Sprague-Dawley-Rolfsmeyer rats at 1, 5, 10, 15 and 20 days of lactation and found to be 476, 523, 762, 553 and 564 MRC mU per gland (5 rats on each day of lactation). A control group of normal virgin rats had 438 MRC mU per gland. These experiments indicate that at day 10 of lactation TCT content of the gland is significantly (P < 0.05) higher than any other day. The possible explanation of TCT accumulation is that during lactation animals undergo a mild hypocalcaemia due to large amounts of calcium drain in milk. Hypocalcaemia and lack of hypercalcaemic stimulation of TCT secretion have been reported to cause TCT accumulation in the thyroid gland. Though gland content does not necessarily reflect secretory status of a hormone, it is possible that less TCT is discharged from the gland during the middle of lactation.

Effect of decreased dietary protein on the rate of thyroid hormone secretion and food consumption in rats

One hundred and twenty albino female rats (Sprague-Dawley-Rolfsmeyer) were divided into five equal groups. Rates of thyroxine secretion (TSR) and food consumption were determined during the control period, and 10 and 25 days after initiation of dietary treatment. Animals in each group served as their own controls for the following modifications of their diet: (1) protein-free diet, (2) 5% protein (casein) diet, (3) 10% protein diet, (4) 15% protein diet, and (5) 20% protein diet. Purina lab chow (23·4% protein) and the 20% casein diet served as control diets. The TSR, the body weight and amount of food consumed were depressed significantly in the group fed on a protein-free diet for 10 and 25 days. The group fed 5% protein diet had a non-significant decrease in TSR as compared with the controls. Similarly, TSR was not reduced by 10, 15 or 20% protein diets. Food consumption decreased significantly in the groups fed a 5, 10 and 15% protein diet, but not in the group on 20% casein. Body weight decreased significantly in the groups on a protein-free diet and on a 5% protein diet.

It would appear from these results that protein content of the diet does not become a limiting factor for TSR until it is lower than 5%. It is suggested that the calorie intake plays a more important role in regard to TSR than a low protein content of the food.