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B Benson

Publications and source records attributed to B Benson.

At least 55 records · Page 3Linked to original sources
PubMed1988

Characterization of a neurohypophyseal hormone-like activity isolated from ovine pineal glands.

The milk-ejecting response of lactating mouse mammary gland tissue to ovine pineal extracts indicated the presence of a neurohormone-like bioactivity in this tissue. After successive fractionation on gel permeation chromatography and reversed-phase liquid chromatography (HPLC) in conjunction with radioimmunoassays (RIA), it was demonstrated that the milk-ejection response to ovine pineal components with an Mr less than 1,000 corresponded to a biologically active peptide sequence that probably differs from that of arginine vasopressin, arginine vasotocin, and oxytocin and from peptides with a COOH-terminal Pro-Arg-Gly-amide ending. Gel permeation chromatography in formic acid appeared also to indicate the presence of a noncovalent interaction of the neurohormone-like bioactivity with proteins (Mr greater than 25,000) of the pineal.

Animals↗
PubMed1988

Possible involvement of the hypothalamic dopaminergic system in the prolactin-inhibitory effects of the pineal gland in blind-anosmic male rats.

The purpose of the present study was to assess whether the pineal-induced suppression of prolactin (PRL) cell activity in blind-anosmic (BA) rats was possibly mediated via the hypothalamic dopaminergic system. Prepubertal male rats were divided into the following groups: sham-operated (Sham), BA and blind-anosmic-pinealectomized (BAP). Animals from each group were sacrificed 1, 4 and 8 weeks after the operations. Blinding and anosmia resulted in pineal-dependent decreases in the weight of the testes, accessory organs and anterior pituitaries at 4 and 8 weeks but not 1 week after the operations. Likewise serum PRL levels were significantly decreased in BA rats at 4 and 8 weeks but this effect was not prevented in BAP rats. Hypothalamic dopamine (DA) turnover in BA rats at 1 week was twice that seen in either the Sham or BAP groups at that time; this effect ended by 4 weeks. There were no effects of any treatment on DA turnover at 8 weeks. Finally, PRL cell sensitivity to DA inhibition was determined by measuring the release of PRL from pituitaries incubated in vitro with either vehicle or 5 x 10(-7) M DA. None of the treatments caused significant alterations in the response to DA, though this must be interpreted with caution since only one dose of DA was used. From these data we conclude that: (1) there is an increase in DA neuron activity that precedes the inhibition of both PRL secretion and the reproductive system in BA rats, and (2) the inhibition of PRL cell activity in these animals is apparently not due to an increase in sensitivity to DA.

Animals↗
PubMed1988

Monoclonal antibodies to surfactant proteins SP28-36 label canine type II and nonciliated bronchiolar cells by immunofluorescence.

The major 28,000- to 36,000-dalton proteins of pulmonary surfactant (SP28-36) have been shown by various techniques to be synthetic and secretory products of alveolar type II cells. Surfactant lipids are also secreted by these cells. Immunocytochemical studies of human and rodent lungs have indicated that nonciliated epithelial cells of small bronchioles appear to contain SP28-36 in their synthetic organelles and secretory granules. Because these observations were obtained with polyclonal antibodies against SP28-36, it was possible that bronchiolar cell staining was due to contaminant antibodies not detected by biochemical analyses. To clarify the role of bronchiolar cells in the metabolism of SP28-36, we have prepared 5 monoclonal antibodies against canine SP28-36. Electrophoresis and immunoblots of surfactant showed that each antibody reacted with SP32 and 36, as well as SP28, the nonglycosylated species. This indicates that the antibodies are directed against the protein rather than carbohydrate moieties of SP28-36. Immunoblot analysis of collagenase-treated SP28-36 showed that the antibodies DS-3 and DS-1 were directed against the noncollagen region of the protein. Immunoblot analysis of whole canine lung homogenates showed that a single protein species was recognized by the antibodies. Immunofluorescence studies of cryostat sections of canine lung showed that both type II and nonciliated bronchiolar cells were specifically labeled with each antibody. These and previous data are consistent with and support the idea that bronchiolar cells synthesize and secrete SP28-36.

Animals↗
PubMed1987

Isolation and sequence of a cDNA clone for the rat pulmonary surfactant-associated protein (PSP-A).

Pulmonary surfactant is composed mainly of phospholipid and two groups of apoproteins. One of these apoproteins is a family of glycoproteins (pulmonary surfactant-associated protein A, PSP-A). We have isolated and sequenced a cDNA clone encoding for rat PSP-A and the full amino acid sequence has been deduced from the nucleotide sequence. The sequence of 56 amino acids at the N-terminus of PSP-A isolated from rats treated with silica was determined independently, and there is complete agreement with the sequence deduced from the cDNA. Isolated rat alveolar type II cells contain two species of mRNA for this protein.

Amino Acid Sequence↗
PubMed1987

Temporal changes in medial basal hypothalamic catecholamines in male Syrian hamsters exposed to short photoperiod.

The gonadal and accessory organ atrophy following transfer of male hamsters from long (LP) to short photoperiod (SP) is preceded by reduced prolactin secretion and involves reductions in hypothalamic LHRH release and catecholamine turnover. These experiments examined the temporal aspects of changes in medial basal hypothalamic/median eminence (MBH/ME) catecholamine turnover rates in male hamsters undergoing SP-induced gonadal atrophy. Hamsters were sacrificed at three, six, nine and twelve weeks of SP exposure. MBH/ME catecholamines and indoleamines were determined by high performance liquid chromatography coupled with electrochemical detection. Reductions in serum prolactin (PRL) levels and increased MBH/ME dopamine (DA) turnover rates were observed at three and six weeks of SP exposure. Both steady state concentrations and turnover rates of norepinephrine (NE) and DA were depressed after nine and twelve weeks of SP exposure, at which time testicular and accessory organ atrophy had occurred. Serotonin (5-HT) and 5-hydroxy-3-indoleacetic acid (5-HIAA) concentrations were insignificantly changed during the period of SP treatment but the 5-HIAA/5-HT ratio was significantly increased after six weeks of SP exposure. It was concluded that increased MBH/ME DA turnover represents an initial, SP-induced neuroendocrine event. This increase in DA turnover probably contributes to the reduced PRL secretion which precedes, and may play a role in the ensuing gonadal and accessory organ atrophy.

Animals↗
PubMed1987

Further studies on the effects of cyclooxygenase inhibitors on compensatory renal growth.

The primary stimulus for compensatory renal growth is unknown. This process may be regulated by a circulating renotropic factor or may reflect a growth response to increased work. Prostaglandins appear to participate in compensatory renal growth as indomethacin has been shown to attenuate increases in both renal mass and function after uninephrectomy in rats. The goal of the present study was to test the effects of other cyclooxygenase inhibitors on compensatory renal growth and to evaluate the effects of indomethacin on renal growth in vitro in response to the purported renotropic factor. Both ibuprofen and meclofenamate retarded compensatory renal growth two days after uninephrectomy in rats (p less than 0.05). The addition of indomethacin to the medium of kidney slices incubating with sera from uninephrectomized rats reduced renal DNA synthesis, whereas indomethacin had no effect on renal growth when added to slices incubating with sera from intact animals. These data provide more support for an important role for prostaglandins in compensatory renal growth.

Animals↗
PubMed1987

Retardation of renal growth and ornithine decarboxylase activity by cyclosporine after uninephrectomy in rats.

Renal transplantation or a partial reduction in renal mass prompts compensatory growth of the kidney, an event that appears to be stimulated by a circulating substance, the purported renotropic factor. This factor may stimulate synthesis of renal polyamines by induction of the rate-limiting enzyme in polyamine metabolism, ornithine decarboxylase. Cyclosporine has been shown to attenuate induction of renal ornithine decarboxylase activity in response to other tropic hormones, such as prolactin, thyroxine, and dexamethasone. These studies were undertaken to evaluate the effects of cyclosporine on induction of renal ornithine decarboxylase activity and growth in response to the serum renotropic factor. Rats were given either 15.0 or 25.0 mg/kg/day or cyclosporine for six days following removal of one kidney. The growth of the remaining kidney was reduced by cyclosporine treatment compared with pair-fed, vehicle-treated control animals. Administration of 25.0 mg/kg/day of cyclosporine also reduced the activity of ornithine decarboxylase in the growing kidney. We conclude that cyclosporine imposes a limitation on the ability of the kidney to grow in response to a reduction in renal mass in rats. The mechanisms of this effect may relate to a blunting of the induction of renal ornithine decarboxylase activity in response to the renotropic factor.

Animals↗
PubMed1987

Short photoperiod depresses castration response in female LSH/SsLaK hamsters.

This study was designed to examine the effects of short photoperiod (SP) exposure on gonadotropin and PRL levels in the presence and absence of estrogen treatment in ovariectomized LSH/SsLak hamsters. In experiment I, regularly cycling hamsters maintained in long photoperiod (14L:10D) were ovariectomized and Silastic capsules containing 2.0-mm columns of estradiol benzoate (EB) implanted simultaneously into half of the animals. On the following day, half of the animals in each treatment group were transferred to SP (8L:16D). After 20 days of SP or long photoperiod (LP) exposure, all animals were sacrificed by decapitation and their sera and pituitaries saved for hormonal determinations. The experimental protocol in experiment II was similar, except that two groups in each photoperiod received estrogen treatments; one group received 2.0-mm implants of 17-beta-estradiol (E2), whereas a second group received 10.0-mm E2 implants. SP treatment effected a reduction in serum LH and FSH levels in the absence of steroid replacement treatment. EB treatment depressed serum gonadotropin levels in LP animals, but did not alter levels in SP hamsters. In experiment II, LP- and SP-treated animals showed similar responses to E2 treatment, although different responses were noted in the two dosage groups. Pituitary gonadotropin contents became progressively decreased with increasing steroid levels and in certain groups showed SP-induced reductions. Serum and pituitary PRL levels increased in response to steroid treatment, but were not affected by SP treatment. In summary, 20 days of SP treatment caused gonad-independent reductions in gonadotropin levels and appeared to reduce the steroid feedback sensitivity of the hypothalamo-pituitary axis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Early short photoperiod effects in female LSH/SsLak Syrian hamsters.

Previous experiments showed that LSH/SsLak female hamsters cease ovarian cyclicity after 2-4 weeks of short photoperiod (SP) treatment. This study was designed to reveal early hormonal and histological changes on day 1 of the estrous cycle (estrus) in SP-treated animals and changes brought about by the SP-induced acyclic condition. Groups of 8-10 animals were killed on day 1 after 0, 4, 8, 12, and 16 days of SP treatment; sera and pituitaries were saved for hormone determinations, and ovaries were prepared for histological analysis. Intraatrial cannulae were inserted into anovulatory animals, and blood samples were withdrawn on the first and second postoperative days; the animals were killed on the third postoperative day. PRL levels were significantly reduced in cycling animals after 16 days of SP exposure and diminished further in acyclic animals. Pituitary PRL did not change in cycling animals, although it was highly depressed in SP-treated acyclic animals. The estrous FSH surge, serum LH levels, and pituitary gonadotropin contents were not affected by SP in cycling animals; in anovulatory animals, pituitary gonadotropin contents were significantly increased, and daily afternoon gonadotropin surges were observed. Uterine weights were reduced in cycling animals and underwent a further reduction after cyclicity ceased. Ovarian analysis revealed that all cycling animals had the same number of recruited follicles, yet significantly fewer corpora lutea and an apparent increase in atretic antral follicles were observed after 16 days of SP exposure. These results suggest that SP-induced cessation of estrous cyclicity occurs abruptly. SP does not alter the secondary FSH surge, but might adversely affect maintenance of follicular growth and depress serum PRL levels.

Anestrus↗
PubMed1987

Surfactant protein of molecular weight 28,000-36,000 in cultured human fetal lung: cellular localization and effect of dexamethasone.

We have examined the effect of explant culture and hormones on the major surfactant associated protein of Mr 28,000-36,000 (SP 28-36) in human fetal lung. Explants of 16- to 23-week gestation lung were maintained for up to 5 days in culture. Polyclonal antibodies raised to SP 28-36 purified from alveolar proteinosis lung lavage were used in immunofluorescence experiments (n = 11). There was no specific fluorescence seen in frozen sections of preculture tissue. In explants cultured without serum or hormones, fluorescence was seen in most epithelial cells lining potential airspaces. In cultures treated with 10 nM dexamethasone and 2 nM T3 much brighter fluorescence was seen in virtually all epithelial cells. Immunofluorescence studies on cell monolayers prepared from explants confirmed that SP 28-36 is found in the cytoplasm of type II cells but not in fibroblasts. The pattern of fluorescence was consistent with the presence of SP 28-36 on rough endoplasmic reticulum. SP 28-36 mRNA was measured in isolated cell populations using a 32P-labeled cDNA probe. mRNA levels were manyfold higher in type II cell preparations (purity 78-92%) than in fibroblasts (purity 81-97%). A competitive enzyme linked assay was developed to quantify SP 28-36. The SP 28-36 content of five lungs before culture (17-23 weeks) was less than 0.02 microgram/mg DNA. During explant culture without hormones the SP 28-36 content increased exponentially. Exposure to dexamethasone accelerated the increase in SP 28-36 content. T3, alone or in the presence of dexamethasone, did not influence SP 28-36 content. We conclude that SP 28-36 content is very low in human fetal lung before 24 weeks gestation. Explant culture and treatment with dexamethasone synchronize development of type II cells from epithelial precursors, and induce synthesis of SP 28-36 in type II cells. These findings provide evidence of concomitant regulation by glucocorticoids of the phospholipid synthetic enzymes and the major protein of pulmonary surfactant.

Cells, Cultured↗
PubMed1986

Inhibition of compensatory renal growth by indomethacin.

Renal prostaglandins may be important in the modulation of compensatory renal growth. Reductions in renal mass are associated with increased synthesis of these substances by the remaining kidney, and inhibition of prostaglandin synthesis diminishes renal function in partially nephrectomized animals and in patients with reduced functioning renal mass. We examined the effects of uninephrectomy and treatment with indomethacin on renal prostaglandin E2 and 6-keto prostaglandin F1 alpha concentrations in adult male Sprague Dawley rats. The renal content of these prostaglandins was significantly increased in the remaining kidney two days following uninephrectomy (p less than 0.01). Treatment with 5 mg/kg/day of indomethacin over this period abolished the compensatory increase in renal prostaglandin synthesis and significantly attenuated compensatory increases in renal mass, protein and RNA concentrations (p less than 0.05). No alterations in kidney weight, protein or RNA concentrations were found in intact animals treated with the same dose of indomethacin. These findings suggest renal prostaglandins may participate in the biological events leading to compensatory renal growth.

6-Ketoprostaglandin F1 alpha↗
PubMed1986

Regulation of pulmonary surfactant apoprotein SP 28-36 gene in fetal human lung.

Pulmonary surfactant stabilizes lung alveoli, preventing respiratory failure and hyaline membrane disease in premature infants. In addition to lipids, surfactant contains apoproteins that are thought to be critical for normal surfactant function. We have examined the ontogeny and regulation of the major surfactant-associated protein of molecular mass 28-36 kDa (SP 28-36) in human fetal lung. SP 28-36 was not detected in tissue from second trimester abortuses by either immunoblot analysis or enzyme-linked immunosorbent assay (less than 0.02 microgram per mg of DNA). Levels of mRNA for SP 28-36, assayed by cDNA hybridization, were low or undetectable in all preculture specimens. The concentration of saturated phosphatidylcholine in lung tissue was 30% of the adult value with no apparent increase between 15 and 24 weeks gestation. SP 28-36 content increased during explant culture in the absence of serum and hormones, exceeding adult levels (3.2 +/- 1.0 micrograms per mg of DNA) after 5 days. In cultures treated with triiodothyronine (2 nM) and dexamethasone (10 nM), hormones that regulate phosphatidylcholine synthesis, the increase in SP 28-36 was accelerated (treated/control ratio was 7.1 and 3.4 at 3 and 5 days, respectively). Levels of mRNA for SP 28-36 also increased during culture and were stimulated by hormones (treated/control = 8.6 and 1.9 at 3 and 5 days, respectively). SP 28-36 and its mRNA increased similarly in the presence of dexamethasone alone, whereas triiodothyronine alone had no apparent effect. The molecular weight and charge pattern was similar for SP 28-36 of adult and cultured fetal tissue. These findings indicate that expression of the SP 28-36 gene is low during the second trimester, increases during explant culture, and is accelerated by glucocorticoid treatment.

Apoproteins↗
PubMed1986

Rapid cessation of estrous cyclicity and depressed castration response in short photoperiod-treated, inbred LSH/SsLaK hamsters.

This study examined the effects of transfer from long photoperiod (LP) to short photoperiod (SP) on the cessation of ovarian cyclicity and the castration response in inbred LSH/SsLak golden Syrian hamsters. Forty-six 8 to 10-wk-old female hamsters were acclimatized in LP (14L:10D; lights on at 0600 h) during which time animals were monitored for regular ovarian cyclicity. Twenty-six animals were transferred to SP (8L:16D; lights on at 0600 h) and examined daily for vaginal discharges. One day after the day of the first missed ovulation, individual SP-exposed animals were bilaterally ovariectomized; concomitantly, an LP control animal in diestrus I underwent the same procedure. Thirty days after ovariectomy, the hamsters were fitted with intra-atrial silastic cannulae. On the following two postoperative days, 0.6 ml blood samples were collected at 0700, 1200, 1400, and 1600 h for SP animals and at 0700, 1400, 1600 and 1800 h for LP controls. On the third day, the animals were decapitated and sera and pituitaries saved for determination of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (PRL) by radioimmunoassay (RIA). All SP-exposed animals displayed their last estrous discharge 14-34 days after transfer to SP (mean = 23.0 +/- 0.8 days). Their ovaries were characterized by the absence of corpora lutea, the presence of large atretic antral follicles, few growing follicles, and interstitium that was stimulated to varying degrees. Total and adjusted pituitary weights were decreased by SP exposure (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Immunocytochemical localization of the major surfactant apoproteins in type II cells, Clara cells, and alveolar macrophages of rat lung.

The adsorptive properties of phospholipids of pulmonary surfactant are markedly influenced by the presence of three related proteins (26-38 KD, reduced) found in purified surfactant. Whether these proteins are pre-assembled with lipids before secretion is uncertain but would be expected for a lipoprotein secretion. We performed indirect immunocytochemistry on frozen thin sections of rat lung to identify cells and intracellular organelles that contain these proteins. The three proteins, purified from lavaged surfactant, were used to generate antisera in rabbits. Immunoblotting of rat surfactant showed that the IgG reacted with the three proteins and a 55-60 KD band which may be a polymer of the lower MW species. Specific gold labeling occurred over alveolar type II cells, bronchiolar Clara cells, alveolar macrophages, and tubular myelin. In type II cells labeling occurred in synthetic organelles and lamellar bodies, which contain surfactant lipids. Lamellar body labeling was increased fivefold by pre-treating tissue sections with a detergent. Multivesicular bodies and some small apical vesicles in type II cells were also labeled. Secondary lysosomes of alveolar macrophages were immunoreactive. Labeling in Clara cells exceeded that of type II cells, with prominent labeling in secretory granules, Golgi apparatus, and endoplasmic reticulum. These observations clarify the organelles and pathways utilized in the elaboration of surfactant. After synthesis, the proteins move, probably via multivesicular bodies, to lamellar bodies. Both lipids and proteins are present in tubular myelin. Immunologically identical or closely similar proteins are synthesized by Clara cells and secreted from granules which appear not to contain lipid. The role of these proteins in bronchiolar function is unknown.

Animals↗
PubMed1985

Structure of canine pulmonary surfactant apoprotein: cDNA and complete amino acid sequence.

The apoproteins of pulmonary surfactant (PSAP) are thought to be critical for normal surfactant function. They bind to surfactant phospholipids and enhance their ability to form surface films in vitro. These acidic glycoproteins have monomeric molecular weights of 36,000, 32,000, and 28,000 (PSAP-36, -32, and -28). Each member of this family of proteins has a similar amino acid composition and their differences in electrophoretic mobility are due in part to glycosylation. We have derived the full amino acid sequence of PSAP-32 from the nucleotide sequence of PSAP cDNA. A cDNA library was prepared from canine lung poly(A)+ RNA and screened with oligonucleotide probes that were based on the NH2-terminal amino acids of PSAP-32 determined by Edman degradation. This protein has the striking feature of collagen-like and non-collagen-like sequences in the same polypeptide chain. There are 24 Gly-Xaa-Yaa triplets, where Yaa is often hydroxyproline. These repeats comprise one-third of PSAP near the NH2 terminus. The remaining two-thirds of PSAP is resistant to bacterial collagenase digestion and contains a possible N-glycosylation site near the carboxyl terminus. The NH2-terminal one-third of PSAP-32 probably contains the cysteine involved in interchain disulfide bonds.

Amino Acid Sequence↗
PubMed1985

Short photoperiod effects on kidney growth in male Syrian hamsters.

The transfer of Syrian golden hamsters from a long to a short photoperiod (SP) leads to reduced circulating levels of several anterior pituitary hormones including thyrotropin stimulating hormone (TSH), luetinizing hormone (LH) and follicle stimulating hormone (FSH), while growth hormone (GH) is unaffected. These hormonal changes are associated with accelerated rates of body weight gain and gonadal atrophy in this species, but the effects on growth of other organs, specifically the kidney, are unknown. In this study, the effect of SP treatment on kidney and body weights of intact and uninephrectomized male Syrian golden hamsters was evaluated. Seventy-two young adult male hamsters were acclimatized to long photoperiod (LP) consisting of a light/dark schedule of 14/10 hours (LD 14:10). Two weeks later one half of the animals were transferred to SP (LD 10:14) Subgroups of six hamsters underwent either left nephrectomy or sham left nephrectomy two, five and eight weeks after transfer to SP and were sacrificed two weeks after surgery. The relative kidney weights (kidney weights/100 g body weight) of the sham operated animals were significantly reduced after seven and ten weeks of SP treatment (p less than 0.01). Absolute kidney weights were depressed after eight (p less than 0.05) and ten weeks in SP. The percentage increase in the weight of the hypertrophied kidney following uninephrectomy was unaffected by SP. Differences in body weights were due to increased fat in SP-treated hamsters; nonetheless, the logs of kidney and body weights were highly correlated in both LP (r = 0.73) and SP (r = 0.78). Lean body weights, determined by body compositional analysis, were less well correlated with kidney weights in LP (r = 0.53) and unrelated in SP (r = 0.16). The mechanism retarding kidney growth was not elucidated, but may include SP-induced changes in TSH, LH, or a specific LH-like pituitary renotropin proposed by Nomura et al. (1982). The observation that compensatory renal growth proceeds despite inhibition of kidney growth in intact animals suggests that separate mechanisms regulate these processes.

Animals↗