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Biomedical subjects

M D Turner

Publications and source records attributed to M D Turner.

At least 19 recordsLinked to original sources
PubMed1992

Exocytosis from permeabilized lactating mouse mammary epithelial cells. Stimulation by Ca2+ and phorbol ester, but inhibition of regulated exocytosis by guanosine 5'-[gamma-thio]triphosphate.

Lactating mouse mammary epithelial cells secrete large amounts of milk protein via constitutive or regulated exocytotic pathways. Secretion through both pathways was quantified by assaying the release of [35S]methionine-labelled trichloroacetic acid-precipitable proteins from digitonin-permeabilized secretory acini isolated from mammary glands of 10-day-post-partum lactating mice. Protein secretion from the isolated permeabilized cells was either Ca(2+)-dependent (regulated) or Ca(2+)-independent (constitutive). In both cases there was a requirement for ATP. Addition of the phorbol ester phorbol 12-myristate 13-acetate (PMA) caused a marked increase in the percentage protein secretion from the cells in a Ca(2+)-independent manner. However, the non-hydrolysable GTP analogue guanosine 5'-[gamma-thio]triphosphate (GTP[S]) caused a partial inhibition of Ca(2+)-dependent exocytosis, while having no significant effect on Ca(2+)-independent exocytosis. Thus the GTP[S] is exerting its effect on the regulated pathway at a site subsequent to protein sorting and packaging into secretory vesicles at the trans-Golgi network.

Adenosine Triphosphate↗
PubMed1992

Proteins are secreted by both constitutive and regulated secretory pathways in lactating mouse mammary epithelial cells.

Lactating mammary epithelial cells secrete high levels of caseins and other milk proteins. The extent to which protein secretion from these cells occurs in a regulated fashion was examined in experiments on secretory acini isolated from the mammary glands of lactating mice at 10 d postpartum. Protein synthesis and secretion were assayed by following the incorporation or release, respectively, of [35S]methionine-labeled TCA-precipitable protein. The isolated cells incorporated [35S]methionine into protein linearly for at least 5 h with no discernible lag period. In contrast, protein secretion was only detectable after a lag of approximately 1 h, consistent with exocytotic secretion of proteins immediately after passage through the secretory pathway and package into secretory vesicles. The extent of protein secretion was unaffected by the phorbol ester PMA, 8-bromo-cAMP, or 8-bromo-cGMP but was doubled by the Ca2+ ionophore ionomycin. In a pulse-label protocol in which proteins were prelabeled for 1 h before a chase period, constitutive secretion was unaffected by depletion of cytosolic Ca2+ but ionomycin was found to give a twofold stimulation of the secretion of presynthesized protein in a Ca(2+)-dependent manner. Ionomycin was still able to stimulate protein secretion after constitutive secretion had terminated. These results suggest that lactating mammary cells possess both a Ca(2+)-independent constitutive pathway and a Ca(2+)-activated regulatory pathway for protein secretion. The same proteins were secreted by both pathways. No ultrastructural evidence for apocrine secretion was seen in response to ionomycin and so it appears that regulated casein release involves exocytosis. Ionomycin was unlikely to be acting by disassembling the cortical actin network since cytochalasin D did not mimic its effects on secretion. The regulated pathway may be controlled by Ca2+ acting at a late step such as exocytotic membrane fusion.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1985

Electrophoretic studies of human upper gastrointestinal mucosal acid proteinases.

The pattern of acid proteinase zymogens, seven pepsinogens (Pg) and slow moving protease (SMP), in normal human gastric mucosa has been reported. No significant differences were found in appearance of individual pepsinogens in oxyntic mucosa in the two sexes, but in pyloric mucosa, Pg 3 occurred significantly more often in men. Rapidly migrating pepsinogens (constituents of Group I pepsinogens) were seen in pyloric mucosa as well as in oxyntic mucosa. The duodenal mucosa contained small amounts of proteinases, the activity being largely confined to the slower moving proteinases (constituents of Group II pepsinogens).

Adult↗
PubMed1984

Experimental small bowel transplantation utilizing cyclosporine.

Cyclosporine prolonged the survival of ectopic small bowel allografts in a canine model. A 9-fold increase in mean survival as compared with controls was obtained. Addition of prednisone to cyclosporine did not result in further graft prolongation, but improved the gross and histological appearance of the allograft. Monitoring the motility and histology of the allograft appears to be useful in predicting approaching rejection. Xylose absorption was not helpful in this regard. A new technique for measuring fat absorption in the transplant is described. Following allografting, fat absorption is resumed by 14 days posttransplantation.

Animals↗
PubMed1983

Studies on human gastric mucosal zymogen granules and their zymogens.

Intact human gastric mucosal zymogen granules (ZG) were detected in specimens from surgical resections of one patient with gastric adenocarcinoma and two with benign gastric ulcer. Both large ZG with unilaminar membranes and smaller ZG with trilaminar membranes were identified by electron microscopy. The zymogens in the ZG and in mucosal extracts were separated by gel electrophoresis. Slow-moving Protease (SMP) was seen in the whole mucosal extracts but was absent from ZG. One specimen of pyloric mucosa showed a striking absence of ZG. Despite the absence of ZG, pyloric mucosa showed Pepsinogens 2-5 (constituents of PG I) as well as Pepsinogens 6 and 7 (constituents of PG II) and SMP.

Cytoplasmic Granules↗
PubMed1983

"COLO 357," a human pancreatic adenosquamous carcinoma: growth in artificial capillary culture and in nude mice.

The human pancreatic cancer cell line COLO 357 has been xenografted s.c. in athymic Swiss mice. The xenografts grew well to form typical adenosquamous carcinomas. The cells were placed in a perfused artificial capillary system where they formed a solid tumor mass which survived for 7 weeks. In this system, the cells consumed glucose and released enzymes and carcinoembryonic antigen into the extracapillary space.

Adenocarcinoma↗
PubMed1982

Ureteral splints: results of a survey.

The results of a survey concerning ureteral splints are reported. Of the respondents 70 per cent preferred the term splint to stent. There was general agreement that a splint should be used in any complicated pyeloplasty as well as in any patient undergoing an operation on the ureter or ureteropelvic junction draining a solitary kidney. Additionally, use of a splint after repair of ureteral injuries by a general urologist was believed advisable. Splints are not absolutely necessary in uncomplicated pyeloplasties and in most simple ureteroneocystostomies. Most urologists use ureteral splints, and believe that they do little or no harm and rather consistently terminate in a good postoperative result.

Humans↗
PubMed1982

Establishment and characterization of two human pancreatic cancer cell lines tumorigenic in athymic mice.

Two human pancreatic cancer lines, RWP-1 and RWP-2, have been established from 2 patients with primary pancreatic cancer metastatic to the liver. The patients' tumors, the xenografted tumors, and tumors obtained by inoculation of nude mice with cultured RWP-1 and RWP-2 cells are all moderately-well-differentiated ductal cell adenocarcinomas. Ultrastructural analysis supports the tissue histopathology findings. Xenografts of RWP-1 tumors double every 10 days, whereas the doubling time of RWP-2 xenografts is 22 days. Both tumors contain mucin. RWP-1 and RWP-2 cells have a doubling time in culture of 45 hr and form colonies in soft agar. RWP-1 cultures appear to be morphologically heterogeneous; two distinct epithelial cell types can be identified. RWP-1 and RWP-2 have modal chromosome numbers of 64 and 62, respectively. Appreciable levels of glucose-6-phosphate dehydrogenase and lactic dehydrogenase were found in both cell lines and xenografts. RWP-1 and RWP-2 cells produce appreciable amounts of carcinoembryonic antigen, 1090 and 414 ng/10(6) cells, respectively.

Adenocarcinoma↗
PubMed1978

Blood flow distribution in dogs during hypothermia and posthypothermia.

Blood flow distribution in tissues of mongrel dogs during hypothermia was studied with radionuclide-tagged microspheres. The animals were cooled at 21 degrees C and rewarmed under thiamylal sodiuni anesthesia. During hypothermia, cardiac output fell to 20% of the control; the highest rate of blood flow relative to normothermic values was observed in the subendocardium of the left ventricle, and the lowest in the hypophysis. Each tissue showed specific reactions to hypothermia. During hypothermia the myocardial and brain-stem blood flows were about 40% of the control; almost all of the digestive tract, striated muscle, adrenal gland, and hypophysis blood flows were maintained at 20% or less of the control. After rewarming, cardiac output recovered to values significantly lower than control. The myocardium, brain, renal cortex, and striated and smooth muscle recovered to control levels; however, blood flow to the digestive organs, bronchial artery flow to the lung, and flow to the endocrine organs did not completely recover by 2 after rewarming.

Animals↗
PubMed1976

Hemorrhagic shock in dogs. Comparison of treatment with shed blood alone versus shed blood plus Ringer's lactate: intravascular pressures, cardiac output, oxygen consumption, arteriovenous oxygen differences, extracellular fluid PO2, electrolyte changes, and survival rates.

The purpose of our study of hemorrhagic shock in dogs was to examine the efficacy of adding Ringer's lactate to shed blood replacement in increasing animal rates. The standard Wiggers' hemorrhagic shock technic was used in two groups of ten animals each. Intravascular pressures, cardiac outut, oxygen consumption, arteriovenous oxygen differences, extracellular fluid PO2 and pH, electrolyte changes, and survival rates were determined. There was a positive correlation between changes in cardiac output, central venous oxygen content, and PO2 and extracellular fluid PO2 as measured using subcutaneously implanted Silastic tubing and perforated plastic balls. Four of the dogs that received shed blood alone survived, whereas five of the dogs that received shed blood plus Ringer's lactate survived. This difference was not statistically significant.

Animals↗