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Biomedical subjects

N Daniel

Publications and source records attributed to N Daniel.

At least 37 records · Page 2Linked to original sources
PubMed1996

Involvement of a subset of tyrosine kinases and phosphatases in regulation of the beta-lactoglobulin gene promoter by prolactin.

This study used pharmacological intervention to provide support for a role of kinases and phosphatases in prolactin transactivation of a milk protein gene. It was based on transient cotransfection using a rabbit prolactin receptor expression plasmid and a beta-lactoglobulin promoter/CAT reporter construct. In cotransfected CHO cells, herbimycin A and tyrphostin, two tyrosine kinase inhibitors, were able to decrease the CAT response by over 50%, along with tyrosine phosphorylation of cellular proteins, whereas genistein and lavendustine were without effect on lactoglobulin transactivation. Orthovanadate, an inactivator of tyrosine phosphatases, was able to substitute for prolactin in inducing the CAT response. Staurosporine, a non-specific kinase inhibitor, was able, when used at low concentrations (10 nM), to augment the prolactin response strikingly. Threonine/serine kinases do not appear to be involved early in beta-lactoglobulin promoter transactivation, since four C-kinase inhibitors and okadaic acid a threonine/serine phosphatase inhibitor, were without substantive effect. We conclude that specific tyrosine kinases are responsible for most of the signal transduction from the prolactin receptor to the beta-lactoglobulin gene promoter.

Animals↗
PubMed1995

Role of tyrosine phosphorylation in potassium channel activation. Functional association with prolactin receptor and JAK2 tyrosine kinase.

Chinese hamster ovary (CHO) cells, stably transfected with the long form of the prolactin (PRL) receptor (PRL-R) cDNA, were used for PRL-R signal transduction studies. Patch-clamp technique in whole cell and cell-free configurations were employed. Exposure of transfected CHO cells to 5 nM PRL led to the increase of Ca(2+)- and voltage-dependent K+ channel (KCa) activity. The effect was direct as it was observed also in excised patch experiments. A series of tyrosine kinase inhibitors was studied to investigate the possible involvement of protein tyrosine kinases in KCa functioning and its stimulation by PRL. Genistein, lavendustin A, and herbimycin A decreased in a concentration and time-dependent manner the amplitude of the KCa current in whole cell and the open probability of KCa channels in cell-free experiments. The subsequent application of PRL was ineffective. The protein tyrosine phosphatase inhibitor orthovanadate (1 mM) stimulated KCa channel activity in excised patches, indicating that channels can be modulated in opposite directions by protein tyrosine kinase and protein tyrosine phosphatase. Moreover, in whole cell experiments as well as in excised patch recordings, anti-JAK2 tyrosine kinase antibody decreased the KCa conductance and the open probability of the KCa channels. Subsequent application of PRL was no longer able to stimulate KCa conductance. Immunoblotting studies using the same anti-JAK2 antibody, revealed the constitutive association of JAK2 kinase with PRL-R. Preincubation of anti-JAK2 antibody with the JAK2 Immunizing Peptide abolished the effects observed using anti-JAK2 antibody alone in both electrophysiological and immunoblotting studies. We conclude from these findings that these KCa channels are regulated through tyrosine phosphorylation/dephosphorylation; JAK2 tyrosine kinase, constitutively associated with PRL-R, is implicated in PRL stimulation of KCa channels.

Animals↗
PubMed1995

The rabbit mammary gland prolactin receptor is tyrosine-phosphorylated in response to prolactin in vivo and in vitro.

We report the first in vivo study demonstrating tyrosine phosphorylation of mammary gland proteins including the prolactin receptor, in response to the injection of prolactin. Immunoblotting of mammary gland membrane extracts revealed that subunits of 200, 130, 115, 100, 90, 70, and 45 kDa display increased tyrosine phosphorylation within 5 min of prolactin administration. The 100-kDa component was identified as the full-length prolactin receptor by a variety of means including immunoprecipitation and immunoblotting with monoclonal (U5, 917, 110, and 82) and polyclonal (46) antibodies to the prolactin receptor. Maximal receptor phosphorylation was seen within 1 min of hormone injection, and to obtain a strong response it was necessary to deprive rabbits of their endogenous prolactin for 36 h. Rapid tyrosine phosphorylation of the full-length receptor was verified by its demonstration in Chinese hamster ovary cells stably transfected with rabbit prolactin receptor cDNA. Both in vivo and in vitro, the phosphorylation signal was transient, being markedly reduced within 10 min of exposure to prolactin. Tyrosine-phosphorylated receptor was shown to be associated with JAK 2 by immunoblotting of receptor immunoprecipitated from transfected Chinese hamster ovary cells with polyclonal 46. A 48-kDa ATP-binding protein was also shown to be associated with the mammary gland receptor by U5 or polyclonal 46 immunoprecipitation of receptor complexes following covalent labeling with [alpha-32P]azido-ATP. Our demonstration of prolactin receptor tyrosine phosphorylation raises the possibility of signaling pathways regulated by receptor/SH2 protein interaction, which would facilitate prolactin specific responses. The fact that a period of hormone deprivation is needed for significant hormone triggered receptor phosphorylation indicates that the mammary gland receptor exists in a largely desensitized state in vivo, analogous to the related growth hormone receptor.

Adenosine Triphosphate↗
PubMed1995

Prolactin induces growth inhibition and promotes differentiation of CHO cells stably transfected with prolactin receptor complementary DNA.

We have characterized a stable and functional transfectant of the rabbit prolactin receptor in Chinese hamster ovary cells, and investigated the action of prolactin (PRL) on the growth and differentiation of this transfectant (clone E32). PRL induced a significant inhibition of E32 cell proliferation. Growth inhibition correlated with gene induction of the molecular marker of ovarian differentiation cholesterol side chain cleavage P450 (P450scc). Both effects were inversely proportional to cell confluence. The limits and potential development of such transfected cellular systems are discussed.

Animals↗
PubMed1995

Functional results of the double-stapled ileoanal reservoir.

BACKGROUND: The preferred method for creation of an ileoanal reservoir is still controversial. We prospectively studied the functional and physiologic outcome of our patients who underwent a double-stapled ileoanal reservoir (DSIAR). STUDY DESIGN: All consecutive patients who underwent restorative proctocolectomy with a DSIAR between 1988 and 1993 were evaluated. Functional results were assessed by questionnaires and anal manometry preoperatively and two, 12, and 24 months postoperatively. RESULTS: One hundred forty patients (90 males and 50 females) with a mean age of 40.7 (range, 12 to 71) years were evaluated. Of these, 107 patients (77 percent) had ulcerative colitis, 21 (15 percent) had familial adenomatous polyposis, six (4 percent) had indeterminate colitis, and six (4 percent) had a post-operative diagnosis of Crohn's disease. One hundred twenty-four (95 percent) of the 131 patients with closed stomas were available for functional and manometric evaluation at a mean follow-up period of 24 months. A 32 percent decline in the mean resting pressure (from 71.3 +/- 4 to 48.2 +/- 3.4 mm Hg) occurred early after DSIAR (p < 0.001) with partial recovery by 24 months. The maximal internal sphincter resting pressure showed a 39 percent decline (from 90.8 +/- 4.9 to 55.3 +/- 5.7 mm Hg, p < 0.005) with recovery after 12 months. There were no significant changes in the length of the high-pressure zone or mean or maximal squeeze pressures. A mean of 5.4 (two to 13) bowel movements occurred during the day and a mean of 1.2 (zero to four) occurred at night. Perfect or almost perfect continence was reported during the day and night, respectively, by 95 and 92 percent of the patients. Overall perioperative complications occurred in 30 patients (21 percent) including septic complications in eight (6 percent), and pouchitis in eight (6 percent). There was one postoperative death (0.7 percent). CONCLUSIONS: Double-stapled ileoanal reservoir is associated with good subjective functional and objective physiologic results and has acceptable rates of morbidity and mortality.

Adenomatous Polyposis Coli↗
PubMed1994

Congo red protects against toxicity of beta-amyloid peptides on rat hippocampal neurones.

beta-Amyloid peptides are neurotoxic when applied to primary cultures of hippocampal neurones from the embryonic rat. This neurotoxic effect can be inhibited completely by certain disazo dyestuffs. The most potent of these are Congo Red and Congo Rubin, whilst Direct Garnet and sodium 4-aminonaphthalene-1-sulphonate are inactive. Congo Red also inhibits the neurotoxic effects of the human pancreatic amyloidogenic peptide amylin. It is postulated that these dyes, by interacting with the beta-pleated sheet structure of amyloidogenic peptides, prevent aggregation and hence neurotoxity.

Amyloid↗
PubMed1994

Prospective, randomized, endoscopic-blinded trial comparing precolonoscopy bowel cleansing methods.

PURPOSE: Recent reports have suggested that precolonoscopy bowel preparation is easier to tolerate if a small volume solution is used. Therefore, the aim of this study was to compare three oral solutions for colonoscopy to determine any changes in either patient compliance or cleansing ability. METHODS: Four hundred fifty patients were prospectively randomized to receive either a standard 4-liter polyethylene glycol solution, a newer sulfate-free 4-liter polyethylene glycol solution, or a 90-ml oral sodium phosphate preparation. Before and after bowel preparation all patients were weighed, and serum electrolytes as well as phosphate, magnesium, calcium, and osmolarity were measured. In addition, a detailed questionnaire was used to assess side effects and patient satisfaction. Endoscopists blinded to the type and quantity of preparation used scored the type of residual stool and the percentage of bowel wall visualized for each segment of colon and for the overall examination. Nurses recorded all procedure times as well as the quantity of irrigation and aspiration. RESULTS: Four hundred twenty-two age-matched and sex-matched patients completed all phases of the trial. There were no clinically significant changes in weight or in any biochemical parameters. There was, however, asymptomatic hyperphosphatemia in the sodium phosphate group (P < 0.01). The length of time to the cecum was similar for all three groups, with a higher volume of fluid suctioned for sodium phosphate (P < 0.01). Overall, endoscopists scored sodium phosphate as "excellent" or "good" in 90 percent vs. 70 percent and 73 percent after the polyethylene glycol or sulfate-free lavage, respectively (P < 0.01). Particulate or solid stool was found in all segments of the colon more frequently after both large volume preparations than after sodium phosphate (P < 0.05). There were no significant differences in the frequency or intensity of any of the 11 side effects questioned. Eighty-three percent of the patients who received the sodium phosphate preparation stated they would take this same preparation again, vs. only 19 percent and 33 percent for polyethylene glycol and the sulfate-free lavage, respectively (P < 0.01). CONCLUSION: The smaller volume oral sodium phosphate was not associated with any clinically significant problem, caused no increase in the incidence of side effects, was preferred by patients, and was more effective in colonic cleansing. However, the hyperphosphatemia seen may limit its use in patients with impaired renal function.

Adolescent↗
PubMed1994

Early effects of PRL on ion conductances in CHO cells expressing PRL receptor.

Chinese hamster ovary (CHO-K1) cells were stably transfected with prolactin (PRL) receptor cDNA. These cells (CHO-E32) expressed the long form of functional PRL receptor. Using microfluorimetric and patch-clamp techniques, we have investigated the effects of PRL on intracellular Ca2+ concentration ([Ca2+]i) and membrane ion conductances. Exposure of CHO-E32 cells to 5 nM PRL resulted in an increase in [Ca2+]i. Two types of response were observed: 1) a stimulation of Ca2+ entry and 2) an intracellular Ca2+ mobilization. As PRL inhibited voltage-activated Ca2+ current, the PRL-induced Ca2+ increase does not involve voltage-activated Ca2+ channels. PRL also increased a charybdotoxin-sensitive Ca(2+)-dependent K+ conductance. Simultaneous measurements showed that PRL hyperpolarized the membrane potential before increasing intracellular Ca2+ levels. In voltage clamp, hyperpolarizing voltage steps were associated with increased Ca2+ concentrations, whereas depolarizing voltage steps decreased [Ca2+]i. Cell-free patch-clamp experiments showed that PRL directly stimulates K+ channel activity. Our results suggest the existence of a regulatory complex involving a protein kinase tightly associated with the Ca(2+)-activated K+ channels and that PRL stimulates these channels by means of the activation of protein kinase. The resulting hyperpolarization stimulates Ca2+ entry, probably through voltage-insensitive nonspecific channels.

Animals↗
PubMed1994

Prolactin receptor and signal transduction to milk protein genes.

After cloning of the mammary gland prolactin (PRL) receptor cDNA, a functional assay was established using co-transfection of PRL receptor cDNA together with a milk protein promoter/chloramphenicol acetyl transferase (CAT) construct in Chinese hamster ovary (CHO) cells. Different mutants of the PRL receptor were tested in this CAT assay to delimit the domains in the receptor necessary for signal transduction to milk protein genes. In CHO cells stably transfected with PRL receptor cDNA, high numbers of PRL receptor are expressed. By metabolic labeling and immunoprecipitation, expressed PRL receptor was identified as a single species of 100 kDa. Using these cells, we analyzed the effects of PRL on intracellular free Ca++ concentration. PRL stimulates Ca++ entry and induces secondary Ca++ mobilization. The entry of Ca++ is a result of an increase in K+ conductance that hyperpolarizes the membranes. We have also analyzed tyrosine phosphorylation induced by PRL. In CHO cells stably transfected with PRL receptor cDNA, PRL induced a very rapid and transient tyrosine phosphorylation of a 100-kDa protein which is most probably the PRL receptor. The same finding was obtained in mammary membranes after PRL injection to lactating rabbits. Whereas tyrosine kinase inhibitors genistein and lavendustin were without effect, PRL stimulation of milk protein gene promoters was partially inhibited by 2 microM herbimycin in CHO cells co-transfected with PRL receptor cDNA and the beta lactoglobulin CAT construct. Taken together these observations indicate that the cytoplasmic domain of the PRL receptor interacts with one or several tyrosine kinases, which may represent early postreceptor events necessary for PRL signal transduction to milk protein genes.

Animals↗
PubMed1993

Perineal rectosigmoidectomy in the elderly.

Between April 1989 and October 1991, 20 consecutive patients underwent perineal rectosigmoidectomy and coloanal anastomosis for full-thickness rectal prolapse. These 16 females and 4 males, with a mean age of 82 (range, 68-101) years, were evaluated by detailed functional assessment and physiologic testing. A grading scale from 0 to 24 was based upon the frequency and type of incontinence, 0 representing full continence. The mean preoperative continence score was 14.5, while the mean postoperative continence score was 8.4. The mean length of resected rectosigmoid was 23 cm. There was one postoperative death and one significant complication, a postoperative pelvic hematoma that required reoperation. There were no full-thickness recurrences at a mean follow-up of 26 months. Six of the 10 patients who underwent preoperative pudendal nerve terminal motor latency (PNTML) testing had evidence of severe neuropathy (latencies greater than 2.5 milliseconds). Prolonged PNTML, however, was not shown to be an accurate predictor of postoperative incontinence because four of the six patients with neuropathy regained excellent to good control. In conclusion, perineal rectosigmoidectomy is a safe operation for the treatment of full-thickness rectal prolapse in the elderly patient. Improved postoperative continence was noted in 90 percent of patients, with improvement seen even in those patients with severe pudendal neuropathy.

Aged↗
PubMed1993

Loop ileostomy is a safe option for fecal diversion.

This study was undertaken to prospectively assess all morbidity and mortality associated with temporary loop ileostomy. Eighty-three consecutive patients of a median age of 45 years required temporary fecal diversion after either ileoanal or low colorectal anastomosis (n = 72), for perianal Crohn's disease (n = 5), or for other reasons (n = 6). All loop ileostomies were supported with a rod, and fecal diversion was maintained for a mean of 10 weeks. To date, 67 patients have had re-establishment of intestinal continuity. Stoma closure was affected through a parastomal incision in 64 patients; in three, a laparotomy was required. The closure was stapled side to side in 49 patients, while a hand-sewn anastomosis was done in the other 18 patients; all skin wounds were left open. The mean length of surgery for ileostomy closure was 56 minutes, and the mean hospital stay was five days. Nine patients (10.8 percent) developed 10 complications, nine of which required hospitalization. Specifically, four patients developed dehydration and electrolyte abnormalities secondary to high stoma output, and two had anastomotic leaks that spontaneously healed following conservative management. One patient developed a superficial wound infection that spontaneously drained itself. One patient developed a partial small bowel obstruction that resolved without surgery after a four-day hospitalization. One stoma retracted after supporting rod removal and prompted premature closure. There was no stomal ischemia, hemorrhage, prolapse, or mortality in this series. Thus, loop ileostomy is a safe way to achieve fecal diversion.

Adolescent↗
PubMed1992

The trophic effect of beta-amyloid 25-35 peptide is not mediated by NK1 or bombesin receptors.

beta-Amyloid peptide and spantide have previously been described to have trophic effects on hippocampal neurones in vitro. We report here that bombesin and [Pro9]-substance P also show a neurotrophic effect on cultured hippocampal neurones. The neurotrophic effect of spantide or a beta-amyloid fragment containing amino acids 25 to 35 was not blocked by addition of the NK1 receptor agonist, substance P or the nonpeptide NK1 antagonist, RP 67580. For the bombesin-related peptides, the antagonist [Tyr4-DPhe12]-bombesin also provokes a trophic response, but the agonist alytesin and the antagonist [Leu13-psi-(CH2NH) Leu14]-bombesin have no effect on neurite growth. These results suggest that the observed trophic responses are unlikely to be mediated by a classical NK1 or bombesin receptor.

Amino Acid Sequence↗
PubMed1991

Colectomy for constipation: physiologic investigation is the key to success.

The results of total abdominal colectomy (TAC) with ileorectal anastomosis as a treatment for colonic inertia (CI) were prospectively assessed. One hundred sixty-three patients were evaluated for chronic constipation between July 1988 and November 1990. Patients underwent pancolonic transit times, anorectal manometry, cinedefecography (CD), and electromyography (EMG). CI was defined as diffuse marker delay on transit study without evidence of puborectalis contraction on CD or EMG. Sixteen patients (10 percent; 15 females and 1 male) with a mean age of 45 years (range, 24-75 years) with CI underwent TAC. Preoperative bowel frequency ranged from three per week to one per month; all 16 patients evacuated only with high doses of laxatives, enemas, or both. TAC was performed with no postoperative mortality or major morbidity; three patients were readmitted four times for successful conservative treatment of partial small bowel obstruction. At a mean follow-up of 15 months (range, 2-35 months), these 16 patients reported a mean frequency of spontaneous bowel evacuations of 3.5 per day (range, one to six per day). Patient satisfaction with the operation was "excellent" or "good" in 15 cases (94 percent). Thorough preoperative physiologic evaluation permits the selection of a small group of patients with CI who may benefit tremendously from TAC.

Adult↗
PubMed1987

Labelling of peripheral-type benzodiazepine binding sites in human brain with [3H]PK 11195: anatomical and subcellular distribution.

The peripheral-type benzodiazepine binding site, erstwhile characterized in the rodent and feline brain, has now been characterized in post-mortem human brain using [3H]PK 11195. The kinetics and pharmacological properties of the binding of this ligand are similar to peripheral-type benzodiazepine binding sites elsewhere. The potency of RO5-4864 for this site in human brain is close to that seen in ruminant and carnivore tissues but considerably lower than in rodent tissues. The regional distribution of these binding sites would suggest a neuronal rather than a glial localization. [3H]PK 11195 bound in a similar fashion to slide-mounted sections of human brain, thus allowing quantitative studies of the regional distribution of peripheral-type benzodiazepine binding sites to be made. The binding sites were distributed heterogeneously, but were restricted to the grey matter. Highest densities of binding sites were found in forebrain structures. The localization was not limited to any functional system, nor did it resemble any previously described transmitter system. The similarities between peripheral-type benzodiazepine binding sites in human and in feline brain in terms of their pharmacological characteristics and their regional and subcellular distribution suggest that the cat, rather than the rat, may be the better model for studying a possible role for this site in human cerebral function.

Animals↗
PubMed1980

Raised cytomegalovirus-antibody level in cerebrospinal fluid of schizophrenic patients.

The serum and cerebrospinal fluid (CSF) of 60 schizophrenic patients and 26 controls were analysed for viral antibody against cytomegalovirus (CMV), vaccinia virus, herpes simplex virus type 1 (HSV), and type A influenza virus. A CSF/serum antibody ratio more than 2 standard deviations above the mean of the controls suggested local antibody production in the central nervous system. 68% of the patients had an increased CSF/serum antibody ratio for CMV antibody, 14% for vaccinia antibody, 4% for HSV antibody, and 15% for influenza virus antibody.

Adolescent↗
PubMedDate not supplied

Comparing opiate users in methadone treatment with untreated opiate users: results of a follow-up study with a Toronto opiate user cohort.

Untreated opiate use is correlated with major social harms and costs in Canada. While methadone treatment has existed in Canada since the 1960s, there is little specific Canadian research on its effects. This paper reports on the one-year follow-up results of a Toronto cohort study of opiate users (N = 114) who were not in treatment at baseline. Sixty-nine people were recruited for re-interviewing. A number of these individuals (N = 29) had entered methadone treatment during the year between baseline and follow-up interviews. Comparisons with respect to social functioning, health status and health care utilization, drug use and related risks, and criminal justice system involvement were made between the follow-up subsample who remained untreated, and the subjects who entered methadone treatment. Differences were found with respect to illegal income generation, illicit opiate and other drug use, illicit drug market activities and emergency care and aspects of socio-economic integration, but no major effects on health and criminal justice status could be shown. Research and policy implications are discussed.

Crime↗
PubMedDate not supplied

[Effect of orally administered bovine lactoferrin and bovine IgG on the establishment of Escherichia coli in the digestive tract of gnotobiotic mice and human newborn infants].

The bacteriostatic effect of the association bovine lactoferrin (LF) and bovine IgG (IgG) was studied in vitro and in vivo against two Escherichia coli strains, S17 and EMO1, isolated from the faecal flora of mouse and man, respectively. These two strains were sensitive in vitro to the bacteriostatic effect of LF + IgG. A kinetic study of the in vivo establishment of E. coli S17 was followed in axenic mice associated with that strain. Seven hours after inoculation, no difference was observed in the faecal level of E. coli between control mice and mice fed the same diet supplemented with LF + IgG. An in vivo study was also carried out in human newborns receiving either maternized milk (Nursie) or the same milk supplemented with LF + IgG during the first 48 h of life. One group of babies was inoculated at birth with E. coli EMO1, while another was not. Between the ages of 1 and 5 days, the kinetics of establishment of the E. coli strains spontaneously found in the digestive tract of non-inoculated babies was not significantly different between the group which received milk supplemented with LF + IgG and that which did not. This result was confirmed in infants inoculated with E. coli EMO1. Likewise, the faecal levels of E. coli EMO1 were similar in the supplemented and non-supplemented babies, and, already from day 1, the population level was high and only slight individual variations between babies of the same group were observed. These findings show that the in vitro bacteriostatic effect of LF + IgG on the growth of E. coli strains is not found in vivo.

Animals↗