Frank J. Weaker

TISSUE SPECIFIC EXPRESSION OF MOUSE TRANSFERRIN DURING DEVELOPMENT AND AGING

Transferrin (TF) is a major plasma protein that binds ferric iron and transports it to all target tissues of the body. This study is the first step to identify the tissue specific expression of the transferrin gene in mice during development, into maturity and throughout the aging process. The transferrin gene expresses mainly in mouse liver, the cerebral hemispheres and cerebellum. In mouse, transferrin is expressed in peritoneal macrophages and in mouse macrophage cell line MO59. At 19 days of gestation, transferrin mRNA is detected in the fetal lung, heart, stomach and kidney. TF mRNA levels increase in liver throughout gestation with maximum expression occurring at 19 days. Transferrin mRNA was detected in placentas of pregnant mice, with levels progressively increasing throughout the term of pregnancy. The levels of liver TF mRNA in mouse vary in a cyclic manner during the development increasing with the aging processes. Because of the dynamic nature of tissue requirements for transferrin during homeostasis the TF gene serves as a promising system for analyzing tissue-specific regulation in vivo during development and aging. Results from this study designate periods in the life-span of the mouse where regulatory mechanisms interacting with the TF gene appear to dynamically alter its expression.

Androgen receptor systems in the brain stem of the primate

The nuclear uptake and retention of [3H]dihydrotestosterone ([3H]DHT) or one of its metabolites was studied in the cerebellum and brain stem of the rhesus monkey. Three days before the injection of the tritiated hormone, we removed both ovaries and the right adrenal gland of 3 female rhesus monkeys under ketamine and halothane or fluothane anesthesia with aseptic surgical procedures. Two days later, we removed the left adrenal gland under similar conditions. Shortly after the second operation, each animal received 100 mg prednisolone sodium succinate. On the day of autopsy, we injected into a femoral vein of each animal 1 microgram of 5 alpha-dihydro[1,2,4,5,6,7-3H]-testosterone (107 Ci/mmol). One of these animals also received an i.v. injection of 100 micrograms/kg body weight of unlabeled DHT to serve as a control. One hour after injection, we rapidly exsanguinated each animal through a femoral venous catheter and perfused the vascular system with approximately 3 1 of Ringers solution through a femoral arterial catheter. The cerebella and brain stems were removed and processed for autoradiography. Unlike in the rat, nuclear uptake and retention of [3H]DHT was found in both motor and sensory systems of these monkeys and in other areas less well defined. These data indicate that there are major species differences in the nuclear uptake and retention of androgen by the cerebellum and brain stem of rats and primates.

A comparison of the suppression of human transferrin synthesis by lead and lipopolysaccharide

Transferrin, as the major iron-transport protein in serum and other body fluids, has a central role in managing iron the body receives. Liver is a major site of transferrin synthesis, and in this study we present evidence that liver synthesis of human transferrin is suppressed by both the toxic metal lead and bacterial lipopolysaccharide, an inducer of the hepatic acute phase response. The responses of intact endogenous transferrin in the human hepatoma cell line HepG2 and chimeric human transferrin-chloramphenicol acetyltransferase genes in transgenic mice were examined. In HepG2 cells, 35S-transferrin protein synthesis and mRNA levels were suppressed by 100 microM and 10 microM lead acetate as early as 24 h after the initial treatment. Yet, synthesis of two proteins known to respond in the hepatic acute phase reaction, complement C3 and albumin, was not altered by the lead treatment. In transgenic mouse liver, lead suppressed expression of chimeric human transferrin genes at both the protein and mRNA levels, but LPS only suppressed at the protein level. The study indicates that lead suppresses human transferrin synthesis by a mechanism that differs from the hepatic acute phase response and that lead may also affect iron metabolism in humans by interfering with transferrin levels.

The Primate Spinal Cord Is a Target for Gonadal Steroids

The nuclear uptake and retention of 3H-dihydrotestosterone (3H-DHT) or one of its metabolites was studied in the spinal cord of the rhesus monkey. Normally-cycling adult female rhesus monkeys which were castrated and adrenalectomized prior to the experiment were injected with 1 μg of 3H-DHT (107 Ci/mmole)/kg body weight and killed 90 minutes later. The spinal cords were removed and segments processed for autoradiography. Nuclear uptake and retention were found in both the visceral and somatic motor systems and, in addition, in the nociceptive system. The data suggest a role for androgen in sexual reflexes and possibly pain perception at the level of the spinal cord in the primate and provide further support for a role of androgen in amyotrophic lateral sclerosis.

Autoradiographic demonstration of binding sites for oestradiol and dihydrotestosterone in the urinary tract of male and female baboons

SummaryBy light microscopic atuoradiography, the kidneys, ureters and urinary bladder of male and female baboons were examined in an effort to define which cells in these three organs were targets for oestradiol (E2) and dihydrotestosterone (DHT). In the parenchyma of the kidney, there was no specific uptake of either 3H-E2 or 3H-DHT, whereas the cortical and medullary connective tissue cells sequestered only 3H-E2. The latter hormone was also found in cells comprising the tunica intima and tunica media of the renal, interlobar and arcuate arteries. The two radiolabelled steroids were concentrated in connective tissue cells of the lamina propria of the ureter and bladder and in the tissue adjacent to smooth muscle fasciculi. Only 3H-DHT was retained by the smooth muscle in these two organs. These observations indicate that specific steroid binding sites are present in the urinary system of the baboon. Their role in the physiology of the kidney, ureter and urinary bladder remains at this point unclear.

Localization of 3H-dihydrotestosterone in the pituitary gland of the rhesus monkey

SummaryThe uptake and retention of radiolabelled dihydrotestosterone by the pituitary gland was examined in the rhesus monkey. Two animals were given an intravenous injection of 1.0μg/kg 3H-dihydrotestosterone (DHT) alone while one monkey received both the labelled androgen and 100μg/kg of unlabelled steroid. One and a half hours later, they were sacrificed. The pituitary glands were removed and processed for autoradiography and immunocytochemistry. Autoradiographic localization of DHT was discernible in the partes nervosa, intermedia and distalis, albeit the highest concentration of radiolabelled cells was noted in the pars distalis. Immunocytochemical staining with antibodies to rat PRL, human TSHβ and ovine LHβ revealed a population of steroid-concentrating cells that contained TSH and a second group that contained LH. None of the cells that reacted with the anti-PRL serum were radiolabelled.

Autoradiographic Localization of 3H-Dihydrotestosterone in the Reproductive Organs of Baboons

The uptake and retention of radiolabelled dihydrotestosterone or one of its metabolites by both the male and female reproductive organs were examined in the baboon 2 male and 2 female baboons were injected intravenously with 1 micrograms/kg body weight of 3H-dihydrotestosterone and 2 animals, 1 male and 1 female, were injected with both labelled and 100 micrograms/kg body weight of radio-inert dihydrotestosterone. 1.5 h the injections, the animals were sacrificed and the uterus, cervix, vagina, uterine tube, labia minora, seminal vesicles, prostate, ductus deferens, and prepuce were removed and treated for autoradiography. The stratified squamous epithelia of the cervix, vagina, labia minora and prepuce demonstrated uptake of label in the germinative, but not in the superficial, cell layers. The columnar cells lining the uterine tube and cervical glands, but not the uterine glands, were labelled. In addition, the nuclei of the cells in the luminal epithelium of the prostate and seminal vesicles contained silver grains. The interstitial cells of the seminal vesicles, prostate and ductus deferens, and the smooth muscle of the prostate and ductus deferens, but not the seminal vesicles, demonstrated an uptake of radioactivity.

Spermatogonia and the cycle of the seminiferous epithelium in the nine-banded armadillo

SummaryThe cycle of the seminiferous epithelium of the nine-banded armadillo can be divided into ten stages. As in most mammals, only one stage is observed per tubular cross-section. The process of spermiogenesis can be divided into thirteen steps according to the development of the acrosomal system and the flagellum. Four generations of spermatogonia are observed in the germinal epithelium: 1) stem cells, 2) type “A”, 3) intermediate, and 4) type “B” spermatogonia. The stem cell is characterized by a highly irregular nucleus and the presence of glycogen in its cytoplasm. The type “A” spermatogonium contains an oblong nucleus with one or two shallow infoldings of the nuclear membrane. The intermediate spermatogonium contains an ovoid nucleus characterized by one or two nuclei and heterochromatin scattered in the nucleoplasm. The nucleus of the type “B” spermatogonium is more spherically shaped with a centrally placed nucleolus and heterochromatin associated with the nuclear envelope.

Ultrastructure of the sertoli and leydig cells in the testes of normal versus protein-calorie malnourished rats

Abstract The morphology of the gonads was examined at the ultrastructural level in 20 to 55 day-old male rats that were protein-calorie malnourished and the results compared to animals fed a standard laboratory diet. The conditions of undernutrition led to a reduction in the growth of the seminiferous tubules. By day 55, the tubules had only developed to a size corresponding to that found in a normal animal less than 30 days of age. A similar retardation was noted in the maturation of the Sertoli and Leydig cells, although the effect of undernutrition on their morphology was evident at an earlier age in the latter cell type. These findings support our previous studies in which it was reported that dietary deficiencies in proteins and calories lead to a prolongation in the time necessary for sexual maturation to occur in male rats.

Do C Cells of the Thyroid Gland of the Baboon Contain Estrogen Receptors

The uptake and retention of radiolabelled estradiol was studied in the thyroid gland of the female baboon. Four baboons were injected intravenously with 1 micron/kg body weight of 3H-estradiol. One animal, which served as a control, received an additional injection of 100 micrograms/kg body weight of unlabelled hormone. One hour after the injections, the animals were killed and the thyroid glands removed and processed for either autoradiography or autoradiography in combination with immunocytochemical staining for C cells. Localization of estradiol was observed in the nuclei of interstitial cells, but not in those of the follicular cells. Nuclei of immunostained calcitonin-containing cells in both the walls of the follicles and the interfollicular compartment were not radiolabelled. This study suggests that estrogen does not regulate calcitonin secretion by the C cells of the thyroid via a classical receptor system.