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Biomedical subjects

J P Mitchell

Publications and source records attributed to J P Mitchell.

At least 19 recordsLinked to original sources
PubMed1992

Improved outcome based on fluid management in critically ill patients requiring pulmonary artery catheterization.

We performed a randomized, prospective trial to evaluate whether fluid management that emphasized diuresis and fluid restriction in patients with pulmonary edema could affect the development or resolution of extravascular lung water (EVLW), as well as time on mechanical ventilation and time in the intensive care unit (ICU), in critically ill patients requiring pulmonary artery catheterization (PAC). PAC was performed on 101 patients. A total of 52 patients were randomized to an EVLW management group using a protocol based on bedside indicator-dilution measurements of EVLW. The other 49 patients were randomized to a wedge pressure (WP) management group in whom fluid management decisions were guided by WP measurements. A total of 89 patients had pulmonary edema (defined as EVLW greater than 7 ml/kg ideal body weight). Except for a clinically unimportant difference in mean age, the two groups were entirely comparable at baseline. The study groups were managed differently, as evidenced by cumulative input-output of 2,239 +/- 3,695 ml (median = 1,600 ml) in the WP group versus 142 +/- 3,632 ml (median = 754 ml) in the EVLW group (p = 0.001). EVLW decreased significantly, and ventilator-days and ICU days were significantly shorter only in patients from the EVLW group. No clinically significant adverse effect occurred as a result of following the EVLW group algorithm. Thus, a lower positive fluid balance, especially in patients with pulmonary edema regardless of cause, is associated with reduced EVLW, ventilator-days, and ICU days.

Algorithms↗
PubMed1991

Fluid balance during pulmonary edema. Is fluid gain a marker or a cause of poor outcome?

STUDY OBJECTIVE: To evaluate the importance of fluid balance and changes in extravascular lung water (EVLW) on survival in the ICU and short-term outcome in patients with pulmonary edema. DESIGN: Retrospective analysis of data (sorting by survival and "treatment received") from a recent randomized controlled trial of fluid restriction in this population. SETTING: Medical ICU of a university-affiliated, tertiary-care medical center. PATIENTS: Eighty-nine patients (from the previously mentioned study) requiring pulmonary artery catheterization with abnormally high EVLW (greater than 7 ml/kg). MEASUREMENTS AND RESULTS: When analyzed by survival, the survivors had no significant fluid gain or change in EVLW but decreased wedge pressure and body weight, compared to nonsurvivors. When analyzed by fluid balance, patients who gained less than 1 L of fluid by 36 hours into the study had a better rate of survival (74 percent) than the rest (50 percent; p less than 0.05). Also, the median duration of days on the ventilator, ICU days, and days of hospitalization was approximately half as long for each variable in the group with less than 1 L of fluid gain. Even accounting for baseline differences in the severity of illness, fluid balance was an independent predictor of survival (p less than 0.05). When analyzed by whether or not EVLW decreased by more than 15 percent between the first and last measurement, only patients with ARDS or sepsis had decreased days on the ventilator and ICU days. CONCLUSIONS: These data support the concept that positive fluid balance per se is at least partially responsible for poor outcome in patients with pulmonary edema and defend the strategy of attempting to achieve a negative fluid balance if tolerated hemodynamically.

Extravascular Lung Water↗
PubMed1990

Site-specific phosphorylation of tyrosine hydroxylase after KCl depolarization and nerve growth factor treatment of PC12 cells.

The phosphorylation and activation of tyrosine hydroxylase was examined in PC12 cells following depolarization with KCl or treatment with nerve growth factor. Both treatments activate tyrosine hydroxylase (TH) and increase enzyme phosphorylation. Site-specific analysis of the tryptic phosphopeptides of TH isolated from [32P]phosphate-labeled PC12 cells demonstrated that the major phosphorylated peptide (termed "H25") did not contain any of the previously reported phosphorylation sites. Phosphoamino acid analysis of this peptide demonstrated that the phosphorylated residue was a serine. Synthetic tryptic peptides containing putative phosphorylation sites were prepared, and subjected to high performance liquid chromatography analysis and isoelectric focusing. The tryptic phosphopeptide containing serine 31 comigrated with the H25 peptide during both of these analytical techniques. The tryptic phosphopeptide produced by the phosphorylation of tyrosine hydroxylase by the recently discovered proline-directed protein kinase and the phosphorylated synthetic phosphopeptide TH2-12 are clearly separated from H25 by this analysis. We conclude that serine 31 is phosphorylated during KCl depolarization and nerve growth factor treatment of PC12 cells and that this phosphorylation is responsible for the activation of tyrosine hydroxylase. Since this site is not located in a sequence selective for any of the "classical" protein kinases, we suggest that a novel protein kinase may be responsible for the phosphorylation of this site. Since serine 31 has a proline residue on the carboxyl-terminal side, the possibility that this kinase may be related to the recently reported proline-directed protein kinase is discussed. Other sites that are also phosphorylated on TH during KCl depolarization include serine 19, which is known to be phosphorylated by calmodulin-dependent protein kinase II. A schematic model for the regulation of tyrosine hydroxylase activity by phosphorylation of the NH2-terminal regulatory domain is presented.

Adrenal Gland Neoplasms↗
PubMed1990

Phosphorylation of synapsin I at a novel site by proline-directed protein kinase.

Previous studies identified synapsin I as a potential substrate for a newly discovered growth factor-sensitive, proline-directed protein kinase originally isolated from rat pheochromocytoma. The present study describes the site-specific phosphorylation of synapsin I by highly purified preparations of proline-directed protein kinase. The incorporation of [32P]phosphate into bovine brain synapsin I was dependent upon both the amount of kinase present and the time of incubation. The maximum stoichiometry of phosphorylation approached 1 mol of phosphate/mol of synapsin I protein. When analyzed by sodium dodecyl sulfate-gel electrophoresis and autoradiography, [32P]phosphate was found to be incorporated into both synapsin Ia and Ib. Phosphoamino acid analysis demonstrated that serine residues were phosphorylated exclusively. Digestion of phosphorylated synapsin I with trypsin followed by high performance liquid chromatography (HPLC) phosphopeptide analysis indicated that the tryptic peptide containing the major phosphorylation site eluted as a single peak at approximately 17% acetonitrile. The primary structure of this phosphopeptide, determined by gas-phase sequencing, was found to be Gln-Ser-Arg-Pro-Val-Ala-Gly-Gly-Pro-Gly-Ala-Pro-Pro-Ala-Thr-Arg-Pro-Pro- Ala-Ser-Pro-Ser-Pro-Gln-Arg. Sequential Edman degradation of this HPLC-purified tryptic phosphopeptide revealed that serine 20 of this peptide was the major phosphorylated residue. This phosphoacceptor site is immediately flanked by a carboxyl-terminal proline residue, an observation that further verifies the proline-directed nature of this protein kinase. The tryptic phosphopeptide corresponds exactly to a sequence in the collagenase-sensitive, proline-rich "tail" region of bovine synapsin I. This novel phosphorylation site is close to but distinct from phosphorylation sites 2 and 3, which are known to be phosphorylated by calcium/calmodulin-dependent protein kinase II and are considered to be of regulatory importance.

Amino Acid Sequence↗
PubMed1990

Strain, social support, and mental health in rural elderly individuals.

This study examined the relationships among social support, life strain, and mental health in a sample of 210 rural elderly individuals. Life strain was operationalized as economic deprivation, illness disability, and ADL impairment. Demographic characteristics had little effect on mental health. Physical health status was highly predictive of life satisfaction and psychological distress among rural elderly individuals. Disability associated with chronic illness and ADL impairment was related to increased reports of symptoms of emotional and psychosomatic distress. Measures of social contacts and instrumental support exerted small to moderate effects on life satisfaction, psychosomatic distress, and emotional distress. Affective support moderated the effects of health-related strain on mental health.

Activities of Daily Living↗
PubMed1989

Identification of a novel proline-directed serine/threonine protein kinase in rat pheochromocytoma.

During investigations of the regulation of tyrosine hydroxylase (TH) by protein phosphorylation, a novel protein kinase activity has been discovered in rat pheochromocytoma. Originally detected as a trace contaminant in preparations of highly purified TH, this novel kinase activity phosphorylated TH at serine 8 in the proline-rich amino-terminal region of the enzyme. This particular site is not phosphorylated by, nor is the amino acid sequence surrounding this site selective for, any of the classical (i.e. well characterized) protein kinases. In this report, we describe the identification, characterization, and partial purification of this novel protein kinase. By utilizing a synthetic peptide corresponding to the amino-terminal region of TH, a selective assay for this protein kinase was developed. The kinase activity utilized ATP and magnesium, although GTP could also be utilized as a phosphate donor. The kinase activity was found to co-purify with TH activity through ammonium sulfate precipitation and DEAE-cellulose chromatography and could be only partially resolved from TH by heparin-agarose affinity chromatography. Substantial kinase activity could be resolved from TH by phosphocellulose chromatography. The novel kinase migrates as a protein with a molecular mass of approximately 45 kDa on gel permeation chromatography as well as sucrose density gradient centrifugation. Studies of site specificity indicate that this Ser/Thr kinase activity appears to be directed by an adjacent (carboxyl-terminal) proline residue, exhibiting a minimal recognition sequence of -X-Ser/Thr-Pro-X-. In addition to TH, this proline-directed protein kinase will also phosphorylate synapsin I, histone H1, and glycogen synthase, suggesting that this kinase may have multiple substrates in vivo. Additional findings indicate that the activity of proline-directed protein kinase is increased transiently in PC12 pheochromocytoma cells following treatment with nerve growth factor. Distinctions between this novel kinase and other well characterized protein kinases can be made on the basis of phosphorylation site specificity, chromatographic behavior, and physical characteristics.

Adrenal Gland Neoplasms↗
PubMed1988

Altered reactivity of the rat adrenal medulla.

Previous studies have suggested that experimental alterations in adrenomedullary reactivity, i.e., changes in catecholamine release in response to a standard dose of acetylcholine, may be partially accounted for by changes occurring at the level of the adrenal medulla itself, independent of both the central nervous system and the innervation of the adrenal gland. The present study was designed to investigate the morphology of adrenal chromaffin cells in rats subjected to chronic hypoglycemia induced by long acting insulin, and to assess this morphology in terms of associated changes in catecholamine content and release. Surgically isolated, perfused adrenal gland preparations were utilized to characterize the functional release of catecholamines from the adrenal medulla. Pretreatment with long acting insulin resulted in a selective depletion of epinephrine stores and acetylcholine-mediated epinephrine release, but did not appear to significantly affect either the levels or the release of norepinephrine. The biochemical effects of long acting insulin persisted for several days after termination of the treatment, exhibiting a gradual recovery over a period of approximately 5 days. Electron microscopic examination of the adrenal chromaffin cells revealed a progressive degranulation and vacuolization of numerous chromaffin cells followed by a compensatory biosynthetic response and a gradual recovery toward the morphology of control cells. The functional release of catecholamines from adrenal chromaffin cells was further examined in preparations of perfused adrenal slices. Acetylcholine-mediated catecholamine release was significantly decreased in slices of adrenal glands prepared from insulin treated rats when compared with that of control animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1986

Immunocytochemical localization of proteins in differentiating tissues of Pisum sativum.

Although there may be documented morphological changes during development, it is obvious that important changes in protein content occur in a vascular plant during the several stages of differentiation. In the absence of the latter information, an approach has been established for the localization of antigenic proteins in developing tissues of Pisum sativum. Monoclonal antibodies were raised to proteins extracted from pea internode tissue, and employed for the localization of three proteins in tissue sections. One of the proteins has two polypeptide subunits with molecular weights of 25,000 and 40,000 daltons, and the antibody binds to both of them. The three monoclonal antibodies produce different patterns of cellular localization in the tissue sections, as visualized by indirect immunocytochemical labeling. In another series of analyses, quantitative and qualitative differences in the protein contents of apical shoot tissue and mature internode shoot tissue have been found. These studies were based on the use of Western blots with both polyclonal (rabbit) antibodies and monoclonal (mouse) antibodies.

Antibodies, Monoclonal↗