Receptor for myo-inositol trisphosphate from the microsomal fraction of Vigna radiata

The microsomal fraction from mung-bean (Vigna radiata) hypocotyl was found to contain Ins (1,4,5)P3- and Ins(2,4,5)P3-binding activity. Preincubation of the microsomal fraction with thiol-containing reagents reduced specific InsP3 binding. A single class of binding site with a Kd value of 1.5 nM and Bmax. of 1.1 pmol/mg of protein was detected. Other myo-inositol phosphates exhibited little affinity for this protein. The binding protein was purified to homogeneity and the molecular mass of the native form recorded as 400 kDa. However, under denaturing conditions the molecular mass was 110 kDa, suggesting that the protein is a homotetramer. That this protein is associated with Ca2+ release was confirmed by including it in proteoliposomes and adding Ins(1,4,5)P3 or Ins(2,4,5)P3. The affinity of Ins(1,4,5)P3 is 3-fold higher than that of Ins(2,4,5)P3. The binding affinity of InsP3 is also reflected in the extent of Ca2+ released from the microsomal fraction. Heparin inhibits binding of InsP3 to the protein, the K1/2 being 0.26 microM. It is also shown that the protein acts as a receptor for InsP3 with characteristics of high affinity and low density.

Novel antagonist to agonist switch in chimeric G protein-coupled alpha-factor peptide receptors

The alpha-factor analog desTrp1,Ala3 alpha-factor (dTA-alpha-factor) acts as an antagonist for both the S. cerevisiae alpha-factor receptor (c-alpha-FR) and the S. kluyveri alpha-factor receptor (k-alpha FR). Chimeric alpha-factor receptors in which a portion (residues 250-303) of the seven hydrophobic segments were derived from the k-alpha FR and the rest from c-alpha FR conferred potent activation of cellular responses by dTA-alpha-factor including induction of FUS1 expression without significantly affecting binding. Chimeric receptors with all hydrophobic segments derived from one receptor did not express sensitivity. We propose that dTA-alpha-factor represents an antagonist that that has an activation energy barrier to activating c-alpha FR and k-alpha FR but which retains a latent potential to act as an agonist.

Noncontiguous domains of the alpha-factor receptor of yeasts confer ligand specificity

The Saccharomyces cerevisiae alpha-factor receptor has a 3400-fold higher affinity for the S. cerevisiae alpha-factor peptide (c-alpha-f) than for the Saccharomyces kluyveri alpha-factor peptide (k-alpha-f) as determined by competition for [3H] c-alpha-f binding. The S. kluyveri alpha-factor receptor has an approximately 2-fold higher affinity for k-alpha-f than for c-alpha-f. The S. kluyveri receptor gene (k-STE2) is incompletely regulated by S. cerevisiae mating type and poorly expressed on the surface of an S. cerevisiae mating type a strain. A chimeric receptor (c/k1) with amino acid residues 1-45 derived from S. cerevisiae and amino acid residues 46-427 from S. kluyveri exhibits the binding specificity of the S. kluyveri receptor. However, chimeric receptors containing residues 1-168 (c/k2) or 1-250 (c/k3) from S. cerevisiae and the remainder from the S. kluyveri receptor exhibit specificities similar to one another, but intermediate between the parent S. cerevisiae and S. kluyveri receptors. The relative ability of c-alpha-f and k-alpha-f to induce growth arrest in strains expressing chimeric receptors parallels relative affinity. Thus, two noncontiguous domains that include putative extracellular loops 1 and 3 and associated transmembrane segments, but exclude the extracellular NH2 terminus and loop 2, appear to contribute to alpha-factor receptor ligand specificity. COOH-terminal regions of the S. kluyveri receptor appear to confer a desensitization defect when expressed in S. cerevisiae. The S. cerevisiae receptor truncated at residue 296 retains ligand specificity for growth arrest.

Differential effects of dichlorodiphenyltrichloroethane analogs, chlordecone, and 2,3,7,8-tetrachlorodibenzo-p-dioxin on establishment of pregnancy in the hypophysectomized rat

Many of the organochlorine pesticides have been shown to elicit estrogenic responses in laboratory animals. Two estrogenic actions, initiation of implantation and maintenance of pregnancy, were examined in progesterone-primed, delayed-implanting, hypophysectomized rats exposed to several polychlorinated hydrocarbons. The insecticide P,P'-dichlorodiphenyltrichloroethane (DDT) was nearly devoid of estrogenic activity for initiating implantation, as was a dichloro analog, 1,1-dichloro-2-[p-chlorophenyl],2-[o-chlorophenyl]ethane (O,P'-DDD), but another such analog, 1,1-dichloro-2-(p-chlorophenyl),2-(o-chlorophenyl)ethylene (O,P'-DDE), was nearly as estrogenic as the O,P'-DDT isomer of DDT and the methoxylated analog methoxychlor. The latter three compounds not only initiated implantation, but maintained pregnancy when given in large (200 mg/kg) and repeated doses. Another insecticide, chlordecone (Kepone) was more estrogenic than any of the DDT analogs and maintained pregnancy with a single dose of 50 mg/kg. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), a toxic contaminant of herbicide production, did not induce implantation at a dose of 125 micrograms/kg, but inhibited the implantation initiated by estrone in 35% of the animals. The mechanism of this antiestrogenicity is unknown but most probably does not involve direct action via the classical estrogen receptor. The possible interference with the normal blastocyst-uterine interactions of these polychlorinated xenobiotics may be an important factor in their being considered reproductive toxins.

Aetiological studies on hospital inpatients with secretory diarrhoea in Calcutta

Twenty-five cases of all age groups with secretory diarrhoea admitted to the Infectious Diseases Hospital, Calcutta were studied. Bacterial enteropathogens were detected by bacteriological examination of the faeces, in each and every case. The main pathogens detected were Escherichia coli and Vibrio cholerae. V cholerae was more commonly associated with severe illness except in the very young, while Esch coli was equally associated with moderate and severe illness. Multiple isolates were more commonly associated with severe illness and single isolates were more common in illness of moderate severity.

Intrathecal buprenorphine for postoperative analgesia in orthopaedic surgery

Sixty patients aged 50-65 years randomly received intrathecally either hyperbaric bupivacaine hydrochloride (one ml) in group A (30 cases) or bupivacaine hydrochloride (one ml) and buprenorphine 300 micrograms in combination in group B (30 cases). They were all scheduled for orthopaedic operations in the lower limbs. Prolonged postoperative analgesia, minimal disturbance of consciousness and respiration were observed in the group that received buprenorphine. The only side-effect found in the buprenorphine group was nausea and vomiting in 10 patients. This study shows that buprenorphine is an effective analgesic suitable for the management of postoperative pain in elderly patients.

Stercoral perforation of the colon proximal to an end colostomy

Stercoral perforation of the colon is rare, and has not previously been reported as a postoperative complication, proximal to an end colostomy. Two such cases are reported; in addition in one the stercoral perforation was recurrent, emphasizing the multifocal nature of the disease. Both cases demonstrate the failure of standard techniques to deal with scybala in the loaded proximal colon. It is, therefore, suggested that intra-operative orthograde colonic lavage is indicated to protect a terminal colostomy from the risk of stercoral perforation in such cases.

Initiation of embryo implantation and maintenance of early pregnancy in the rat by chlordecone (Kepone)

The effect of chlordecone (Kepone), an insecticide/fungicide with reproductive toxicity, on the early stages of pregnancy in the rat was studied. Intraperitoneal injection of chlordecone into adult virgin female Holtzman strain rats before mating, in doses as high as 80 mg/kg, did not prevent fertilization, early development of the embryo to the blastocyst stage, transport of the embryo through the oviduct, or its implantation into the uterus. However, a single dose of 60 or 80 mg/kg, but not 20 or 40 mg/kg, before mating significantly reduced the concentration of progesterone in the serum of rats undergoing normal embryo implantation 5 days later. A dose of 80 mg/kg of chlordecone reduced progesterone levels in the serum by more than 50% within 48 hr in ovariectomized rats with Silastic tubing implants containing crystalline progesterone. This dose of chlordecone induced deciduomata formation in progesterone-primed ovariectomized rats to the same extent as 1 microgram of estradiol benzoate. The minimal effective single dose of chlordecone to initiate implantation of blastocysts in the uteri of hypophysectomized progesterone-primed rats, and to maintain embryo development for at least 5 days, was 50 mg/kg. Daily doses of 20 mg/kg for 3 or 5 days were effective at initiating implantation but did not maintain pregnancy. The latter treatment, however, did not prevent initiation of implantation or embryo development induced by subsequent administration of estrone. The results are consistent with the view that chlordecone is a weak estrogen that has both nongenomic and genomic estrogenic actions.

The cytochrome P450(17) alpha (17 alpha-hydroxylase/C17,20-lyase) activity of the junctional zone of the rat placenta

The cytochrome P450 responsible for androgen synthesis by the placenta during the second half of pregnancy in the rat was studied in intact and hypophysectomized animals. The two activities of P450(17) alpha, 17 alpha-hydroxylase and C17,20-lyase, were limited to the junctional zone. C17,20-Lyase activity was greater with progesterone than with 17-hydroxyprogesterone as substrate. Although the apparent Michaelis constants were similar, progesterone had a higher maximum velocity than 17-hydroxyprogesterone. Regardless of substrate, C17,20-lyase activity was greater with NADPH than with NADH as an electron donor, and there was no additive effect using both cofactors. Administration of human chorionic gonadotrophin (hCG; 10 IU at 09.00 and 21.00 h on days 13 and 14 and at 09.00 h on day 15) to intact females resulted in more than a 50% reduction of enzyme activity when measured on day 15. The same dose of hCG given to hypophysectomized animals with delayed implantation, i.e. pituitary removal on day 3 and implantation induced by oestrone 5 days later, had no effect on placental enzyme activity, but increased that in the ovary. Administration of ovine LH by osmotic minipump (days 11-15) to intact females resulted in abortion in all animals. The same treatment to animals hypophysectomized on day 11 produced abortion in three of four rats; enzyme activity was greatly reduced in the single animal with placentas. In contrast, infusion of LH into hypophysectomized animals with delayed implantation increased placental enzyme activities.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased activity of ovarian thecal cytochrome P450(17 alpha) in the hamster induced by endogenous LH

The in vivo regulatory action of LH on the ovarian androgen synthesizing enzyme cytochrome P450(17 alpha) (17 alpha-hydroxylase/C17,20-lyase) was studied in cyclic golden hamsters. Immunohistochemical studies using anti-porcine testicular cytochrome P450(17 alpha) antibody indicated that the enzyme was limited to thecal cells. Transient removal of the negative feedback action of endogenous steroids by use of aminoglutethimide phosphate produced an increase in endogenous gonadotropins. A single dose (30 mg) of aminoglutethimide on days 1, 2 or 3 of the estrous cycle (day 1 = estrus), increased serum levels of LH, but only for about 12 h. Increases in enzyme activities, which persisted for at least 24 h, followed. Two doses of aminoglutethimide, 12 h-apart, maintained elevated levels of serum LH for about 36 h, and enzyme activities for at least 48 h. However, when the drug was given after the pre-ovulatory surge of LH on proestrus, and again on the morning of estrus, neither serum LH nor enzyme activity levels increased within 24 h. Induced increases in enzyme activity had no effect upon ovulation rate, as determined by the number of oviductal eggs present on the morning of estrus. The results demonstrate clearly a close correlation between serum concentrations of LH and ovarian androgen synthesizing enzyme activity.

Multiple estrogenic action of O,P'-DDT: initiation and maintenance of pregnancy in the rat

The estrogenic action of O,P'-DDT has been known for many years. The majority of studies have used immature or ovariectomized adult rats to demonstrate estrogenic responses that require interaction with an intranuclear receptor and genic expression. However, evidence is accumulating that not all estrogenic effects are mediated by such a receptor; initiation of implantation being one such effect. The present study examined the ability of O,P'-DDT to initiate embryo implantation in the progesterone-primed uterus of a hypophysectomized adult rat. Not only did O,P'-DDT initiate implantation, it also maintained pregnancy for at least 3 days. However, when administered at the time of mating or early after fertilization, the same dosage caused loss of pre-implantation embryos. The results are consistent with the interpretation that O,P'-DDT has multiple estrogenic actions that may involve more than 1 kind of receptor.

The estrogen 2-hydroxylase activity of the gonadotropin-stimulated hypophysectomized immature rat ovary

Using high-performance liquid chromatography and a combination of electrochemical and radiometric flow detection for 2-[14C]hydroxyestradiol, changes in estrogen 2-hydroxylase activity in the microsomal fraction of rat ovarian homogenates were followed. Injection of human chorionic gonadotropin (hCG) at 12-hr intervals to hypophysectomized immature rats stimulated hypertrophy of the theca-interstitial tissue and produced a profound increase in enzyme activity. With the last injection of hCG at 96 hr the peak serum concentration of hCG was reached 12 hr later and then decreased exponentially with a half-time of 13 hr. However, enzyme activity remained elevated for at least 60 hr before beginning to fall. Pregnant mare's serum gonadotropin (PMSG) also produced an increase in activity, which was apparently limited to the thecal-interstitial tissue because freshly removed granulosa cells from the mature follicles had undetectable activity levels. Administration of anti-PMSG antiserum after enzyme activity had been increased resulted in a prompt fall in activity, as did injection of hCG to mimic an ovulatory surge of LH. The results indicate that the thecal-interstitial tissue of the rat ovary has estrogen 2-hydroxylase activity that is dependent upon gonadotropic stimulation for expression.

The effects of different suture techniques on collagen metabolism in experimental distal colonic anastomoses

Two types of suture techniques have been compared in anastomoses of the distal colon in 20 mongrel dogs. They were divided into four groups, each consisting of five dogs. In A and C groups a single layer suture technique, and in B and D groups a two layer suture technique was used. In order to determine tissue hydroxyproline activities at the suture lines, the anastomosed segments were resected on the fifth day in A and B, and on the tenth day in C and D groups. It was observed that the hydroxyproline activities in single layer anastomoses were higher than those of two layer anastomoses with the implication that there was more rapid wound healing.