PubMed Health⌕ Search

Biomedical subjects

K Carter

Publications and source records attributed to K Carter.

15 recordsLinked to original sources
PubMed1992

Role of electric stimulation in bladder evacuation following spinal cord transection.

Neural stimulation is potentially a valuable therapeutic tool in the treatment of neurogenic bladder with detrusor areflexia. We studied 20 dogs in different groups, up to eight months, and compared the effect of electric stimulation with intermittent catheterization, specially during spinal shock phase. We found that early stimulation hastened the return of detrusor activity. When stimulation was delayed, the bladder could still regain its activity, and when the pace-maker was turned off, the detrusor activity was gradually decreased. Neurostimulation can completely empty bladder up to eight months. The lowest A.Ch. content in detrusor muscle was found in intermittent catheterization group and in this group the detrusor strips showed marked supersensitivity to urecholine stimulation than the bladders managed by electric stimulation. Also, we found that electric stimulation reduced the complications caused by intermittent catheterization and protected kidney function.

Animals↗
PubMed1991

Impaired anal sensation and early diabetic faecal incontinence.

Faecal incontinence develops in up to 20% of diabetic patients. To try to determine the relative contributions of sensory and motor neuropathy in this troublesome complication, anorectal function was examined in 10 male diabetic patients with early faecal incontinence (mucus leakage or faecal staining without the need to wear a pad), 10 asymptomatic male diabetic patients, and 10 normal control subjects. Motor function was tested using anal manometry to determine the resting and maximum squeeze pressure, and the functional anal canal length. No significant differences were found between the groups. Sensory function was tested by measuring the mucosal sensitivity to electrical stimulation, and the response to inflation of a balloon in the rectum. In the mid-anal canal position the symptomatic patients had a significantly higher sensory threshold at 6.6 +/- 2.8 mA compared with 3.0 +/- 1.2 mA in the normal control subjects (p less than 0.002), and in the high anal zone symptomatic patients had a significantly elevated sensory threshold at 9.1 +/- 2.0 mA compared with 4.6 +/- 1.6 mA in asymptomatic patients and 3.6 +/- 1.3 mA in the normal control subjects (both p less than 0.001). There were no significant differences in the first sensation of fullness, maximum tolerated volume or percentage fall from resting pressure between the groups on inflation of the balloon. Elevation of the sensory threshold in the upper anal canal is an early abnormality in the development of diabetic faecal incontinence.

Anal Canal↗
PubMed1991

Porcine model for vascular graft studies.

Models for the study of prosthetic vascular graft infection have been studied frequently in the dog and rabbit. We have developed a reproducible swine model to study this problem and its treatment. The cardiovascular system, healing characteristics, and the bloodstream clearance of bacteria in swine more closely resembles those of humans than do other animal models. The low cost and availability of the swine is an additional attractive aspect. One hundred fifty-six farm-bred pigs have undergone infrarenal aortic replacement with a 3-cm segment of 6-mm prosthetic graft over the past two years. Graft infection was produced by (1) direct inoculation of 10(6) Staphylococcus aureus at the time of the surgery or (2) intravenous infusion of bacteria (10(2)-10(6) organisms/mL) immediately after surgery. All animals were sacrificed 1 to 4 weeks later, depending on the study design. Cultures, histology, and electron microscopy were performed on each graft. Anesthetic complications were rare (2.5%). Postoperative complications leading to animal death decreased with increasing experience (11.5%), but included graft thrombosis, bleeding, sepsis, intussusception, and colonic ischemia. Wound infection was the most common cause of morbidity. The swine model is an attractive alternative to that of other animals for the study of prosthetic vascular graft infections. Further details of the operative technique and the comparison to the human and other animal models is discussed.

Animals↗
PubMed1990

Effect of basolateral acidification on the frog oxynticopeptic cell.

The effects of intracellular acidosis induced by acidification of the basolateral (nutrient) perfusate on the structure and function of the oxynticopeptic cell were studied in in vitro frog gastric mucosa. Changing the pH of the unbuffered nutrient perfusate (UNB) from 7.2 to 3.5 acidified the oxynticopeptic cell with no change in potential difference (PD) or resistance (R). Intracellular pH (pHi), PD, and R were 7.05 +/- 0.01, 16 +/- 1 mV, 165 +/- 7 omega.cm2 before and 6.44 +/- 0.01, 16 +/- 2 mV, 170 +/- 9 omega.cm2 after nutrient acidification. Acid secretion (H+) increased from 0.86 +/- 0.07 to 1.88 +/- 0.18 mu eq.cm-2.h-1. Addition of forskolin to tissues perfused with nutrient pH (pHn) 3.5 decreased PD to 2 +/- 2 mV and further increased H+ to 3.07 +/- 0.19 mu eq.cm-2.h-1. By light and electron microscopy oxynticopeptic cells perfused with UNB, pHn 3.5, appeared normal. Oxynticopeptic cells in tissues pretreated with omeprazole and then exposed to UNB, pHn 3.5, had extensive morphological damage. On increasing the pH of the nutrient perfusate from 3.5 to 7.2 there was prompt recovery of pHi in untreated and forskolin-stimulated mucosae (pHi 6.87 +/- 0.06 and 6.85 +/- 0.04) but no recovery of pHi in tissues pretreated with omeprazole or cimetidine (pHi 6.26 +/- 0.04 and 6.44 +/- 0.06, n = 6, 30 min after reexposure to UNB, pHn 7.2). We conclude that in a secreting mucosa intracellular acidification of the oxynticopeptic cell to pHi 6.4 is associated with normal morphology, PD, R, and increased H+, and that intracellular acidosis is not de facto deleterious.

Animals↗
PubMed1989

Effect of CO2 on pHi in rabbit parietal, chief, and surface cells.

We investigated the pH recovery mechanisms in rabbit parietal, chief, and surface cells during pH shifts induced by introduction or removal of exogenous CO2-HCO3-. Intracellular pH (pHi) was measured using the fluorescent dye 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescin (BCECF). Gastric cells were highly purified by density gradient centrifugation and elutriation. When cells suspended in N-2-hydroxyethylpiperazene-N'-2-ethanesulfonic acid (HEPES)-100% O2, extracellular pH (pHo) 7.4, were exposed to 24 mM HCO3- -5% CO2, pHo 7.4, all cells quickly acidified by 0.3-0.4 pH units. Almost complete pH-recovery occurred within 15 min. In parietal cells, 70% of this recovery was dependent on the presence of extracellular Na+ (Nao+) and was blocked by 1 mM amiloride. The Na+-independent recovery was blocked by intracellular Cl- depletion or by 0.4 mM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). In chief cells and surface cells no recovery occurred in the absence of NaO+, and 1 mM amiloride blocked pH recovery in Na+-containing buffer. On removal of HCO3- -CO2, the cells alkalinized, and subsequent pH recovery was fast, substantially extracellular Cl- (ClO-) and DIDS inhibitable in parietal cells but slow and ClO- -independent in chief and surface cells. These results suggest that during intracellular acidification the Na+-H+ exchanger is the major pH regulator in these three gastric cell types even in the presence of HCO3-. During alkalinization the Cl- -HCO3-(OH-) exchanger is the predominant pH recovery mechanism in parietal, but not in chief and surface cells. In parietal cells, this exchanger is also involved in recovery from acidification.

Amiloride↗
PubMed1988

Trypsin proteolysis of the cytochrome d complex of Escherichia coli selectively inhibits ubiquinol oxidase activity while not affecting N,N,N',N'-tetramethyl-p-phenylenediamine oxidase activity.

The cytochrome d complex is one of two membrane-bound terminal oxidases of the Escherichia coli aerobic respiratory chain. Previous studies have shown that this enzyme reconstituted into proteoliposomes rapidly oxidizes ubiquinol-8 as well as the soluble homologue, ubiquinol-1, and that quinol oxidase activity is accompanied by the formation of a transmembrane H+ electrochemical gradient. The enzyme also oxidizes the artificial reductant, N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) with the generation of a H+ electrochemical gradient. In this work, it is established that trypsin digestion of the purified cytochrome d complex cleaves subunit I while subunit II is unaffected. Proteolysis of subunit I is correlated with loss of ubiquinol-8 and ubiquinol-1 oxidase activities. Trypsin digestion has no effect on TMPD oxidase activity. The cytochrome d complex is concluded to possess three distinct active sites for 1) ubiquinol oxidation, 2) TMPD oxidation, and 3) oxygen binding and reduction. Data also suggest that both sites of ubiquinol and TMPD oxidations are located on the periplasmic side of the E. coli membrane while the site of oxygen reduction is on the opposite side.

Animals↗
PubMed1988

Relationships between membrane-bound cytochrome o from Vitreoscilla and that of Escherichia coli.

The cytochrome o terminal oxidases from the bacteria Vitreoscilla and Escherichia coli are structurally and functionally related. They have similar optical spectra, both exhibit ubiquinol-1 oxidase activity and are inhibited similarly. Both enzymes contain four subunits by SDS-polyacrylamide gel electrophoresis analysis and contain protoheme IX and Cu2+ prosthetic groups. Antibodies raised against the oxidase purified from E. coli crossreact with the Vitreoscilla oxidase.

Antibodies, Bacterial↗
PubMed1988

Simple dacryops.

Explore the source record for details and available documents.

Cysts↗
PubMed1988

Effect of ethanol on frog gastric mucosa. Electrophysiologic and morphologic correlations.

The effects of and recovery from luminal ethanol (0%-100%) were assessed in the in vitro chambered frog gastric mucosa. At concentrations of 5%-10%, the potential difference decreased during exposure, but recovered after washout. No gross or light microscopic changes were observed. During exposure to 20%-40% ethanol, potential difference and short circuit current decreased and resistance increased, with only partial recovery after removal of the alcohol. Acid secretion ceased at 20% ethanol and alkalinization of the luminal solution was observed at greater than or equal to 30% ethanol. Microscopy of this group showed discharge of mucus, separation of oxynticopeptic cells from the basal lamina, and slough of surface epithelium. At 60%-100% ethanol, potential difference and short circuit current decreased and resistance increased markedly but there was no recovery. Microscopy showed changes similar to those of the intermediate group (20%-40%), except that surface epithelial cells were fixed to the basal lamina rather than sloughing. The morphologic effects of 100% ethanol in vivo were similar to those in vitro. Pretreatment with 10(-5) M 16,16-dimethyl prostaglandin E2 did not prevent either the electrophysiologic or the histologic changes caused by 20% and 30% ethanol. We conclude that there is a gross discrepancy between the functional and morphologic findings after high concentrations of luminal ethanol.

Animals↗
PubMed1987

Cytochrome b558 monitors the steady state redox state of the ubiquinone pool in the aerobic respiratory chain of Escherichia coli.

The aerobic respiratory chain of Escherichia coli contains two terminal oxidases, the cytochrome o complex and the cytochrome d complex. These both function as ubiquinol-8 oxidases and reduce molecular oxygen to water. Electron flux is funneled from a variety of dehydrogenases, such as succinate dehydrogenase, through ubiquinone-8, to either of the terminal oxidases. A strain was examined which lacks the intact cytochrome d complex, but which overproduces one of the two subunits of this complex, cytochrome b558. This cytochrome, in the absence of the other subunit of the oxidase complex, does not possess catalytic activity. It is shown that the extent of reduction of cytochrome b558 in the E. coli membrane monitors the extent of reduction of the quinone pool in the membrane. The activity of each purified oxidase was examined in phospholipid vesicles as a function of the amount of ubiquinone-8 incorporated in the bilayer. A ratio of ubiquinol-8:phospholipid as low as 1:200 is sufficient to saturate each oxidase. The maximal turnover of the oxidases in the reconstituted system is considerably faster than observed in E. coli membranes, demonstrating that the rate-limiting step in the E. coli respiratory chain is at the dehydrogenases which feed electrons into the system.

Aerobiosis↗
PubMed1985

Reconstitution of the Ubiquinone-dependent pyruvate oxidase system of Escherichia coli with the cytochrome o terminal oxidase complex.

The aerobic respiratory chain of Escherichia coli is branched and contains two terminal oxidases. The chain predominant when the cells are grown with low aeration terminates with the cytochrome d terminal oxidase complex, and the branch present under high aeration ends with the cytochrome o terminal oxidase complex. Previous work has shown that cytochrome d complex functions as a ubiquinol-8 oxidase, and that a minimal respiratory chain can be reconstituted in proteoliposomes with a flavoprotein dehydrogenase (pyruvate oxidase), ubiquinone-8, and the cytochrome d complex. This paper demonstrates that the cytochrome o complex functions as an efficient ubiquinol-8 oxidase in reconstituted proteoliposomes, and that ubiquinone-8 serves as an electron carrier from the flavoprotein to the cytochrome complex. The maximal turnover (per cytochrome o) achieved in reconstituted proteoliposomes is at least as fast as observed in E. coli membrane preparations. Electron flow from the flavoprotein to oxygen in the reconstituted proteoliposomes generates a transmembrane potential of at least 120 mV, negative inside, which is sensitive to ionophore uncouplers and inhibitors of the terminal oxidase. These data demonstrate the minimal composition of this respiratory chain as a flavoprotein dehydrogenase, ubiquinone-8, and the cytochrome o complex. Previous models have suggested that cytochrome b556, also a component of the E. coli inner membrane, is required for electron flow to cytochrome o. This is apparently not the case. It now is clear that both of the E. coli terminal oxidases act as ubiquinol-8 oxidases and, thus, ubiquinone-8 is the branch point between the two respiratory chains.

Cell Membrane↗