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Biomedical subjects

J M Bowes

Publications and source records attributed to J M Bowes.

12 recordsLinked to original sources
PubMed1995

Decreasing the complications of renal osteodystrophy secondary to high phosphorus levels by using an innovative self-monitoring educational program.

We wanted continuous ambulatory peritoneal dialysis (CAPD) and continuous cycling peritoneal dialysis (CCPD) patients to become more cognitive of the complications of high-serum phosphorus levels (> 6.0 mg/dL). The phosphorus self-monitoring program was designed to encourage patients to be more responsible for preventing the complications of renal osteodystrophy. Patients' phosphorus levels were graphed monthly on a poster in the exam room. Additional posters discussed their responsibilities to control phosphorus and the complications associated with hyperphosphatemia. All patients received an informative letter regarding the inception of the program in March 1994 and also were assured total anonymity of their laboratory results. At monthly clinic appointments, they received additional written information on phosphorus and discussed their phosphorus levels. Our teaching method proved effective in our CAPD/CCPD population. In March 1994, 31% of our patients had a phosphorus level greater than 6.0 mg/dL versus 10% in September 1994. The ability of patients to see their monthly progress and the comparison with other patients encouraged much interest and questions regarding phosphorus control.

Adolescent↗
PubMed1991

Depression in recently bereaved prepubertal children.

OBJECTIVE: The purpose of this study was to ascertain depressive symptoms in recently bereaved prepubertal children and compare these symptoms with those of depressed prepubertal children. METHOD: The subjects were 38 children who had recently experienced the death of one but not both of their parents. They had to meet strict inclusion criteria so that the effects of bereavement per se, rather than other significant stressors, could be assessed. The comparison group consisted of 38 hospitalized, depressed children individually matched to each bereaved subject for age, sex, and socioeconomic status. All of the children underwent systematic and comprehensive evaluation. They and their parents were independently evaluated by trained interviewers using the parent and child versions of the Diagnostic Interview for Children and Adolescents. Family histories and basic demographic information were also obtained. RESULTS: The recently bereaved children endorsed many depressive symptoms. Thirty-seven percent of them met the DSM-III-R criteria for a major depressive episode. The depressed children, however, had more depressive symptoms on average than the bereaved children. The factors associated with increased depressive symptoms in the bereaved children were 1) the mother as the surviving parent, 2) preexisting untreated psychiatric disorder in the child, 3) family history of depression, and 4) high socioeconomic status. CONCLUSIONS: A considerable number of the bereaved children developed the clinical symptoms of a major depressive episode immediately after the death of a parent. The relation of these symptoms to the subsequent course of grief and to major depressive disorder remains unknown and should be studied further.

Adult↗
PubMed1990

Dexamethasone suppression test and depressive symptoms in bereaved children: a preliminary report.

Eighteen bereaved children and adolescents were assessed using the dexamethasone suppression test (DST) and the Diagnostic Interview for Children and Adolescents 4 weeks following parental death. Thirty-nine percent had a positive (nonsuppressed) DST. DST-positive subjects reported more DSM-III-R depressive symptoms (6.3 +/- 2.9 vs. 3.9 +/- 2.7, means +/- SD) than DST-negative subjects. Most frequently reported symptoms included dysphoria, loss of interest, sleep disturbance, appetite disturbance, psychomotor disturbance, and morbid and suicidal ideation. Post-dexamethasone cortisol levels were significantly correlated with the total number of depressive symptoms and suicidal ideation.

Adolescent↗
PubMed1983

Characterization of photosystem ii electron acceptors in Phormidium laminosum.

Chlorophyll a fluorescence has been used to monitor the redox state of the primary electron acceptor of photosystem II (PS II) in the blue-green alga Phormidium laminosum during equilibrium titrations. The shape of induction curves measured in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU) have been analyzed. The induction curves were very similar in unfractionated thylakoid membranes and PS II particles. In both, the fast (alpha) phase was sigmoidal, and was followed by a slow (beta) exponential tail. Thus, the structural organization and complexity of the particles (J. M. Bowes and P. Horton, Biochim, Biophys. Acta 680, 127-133 (1982), as indicated by the occurrence of energy transfer between alpha centers and presence of beta centers, must preexist in the membranes. Redox titration of the initial level of fluorescence indicated the presence of a single quencher QH in the unfractionated thylakoids, midpoint potential: Em7.0 approximately -35 mV (n = 1). Thus, the occurrence of a single acceptor is characteristic for P. laminosum and the absence of a low potential acceptor in PS II particles (J.M. Bowes, P. Horton, and D.S. Bendall, FEBS Lett. 135, 261-264 (1981] was not the result of its removal during their preparation. The midpoint potential of Q varied by -60 mV/pH unit in PS II particles and membrane fragments, with a pK at pH greater than 8.5 (particles) and at pH 7.5 (fragments). In PS II particles, DCMU raised the pK by approximately 0.5 pH units. It is argued that the pH dependence of Q is conferred by protonation of a protein which accompanies its reduction rather than protonation of the semiquinone Q X itself.

Chlorophyll↗
PubMed1980

Binary oscillations in the rate of reoxidation of the primary acceptor of photosystem II.

The decay of fluorescence yield following each of a series of saturating laser flashes has been used to monitor the kinetics of reoxidation of the primary acceptor of Photosystem II under conditions of varied redox potential. 1. In dark-adapted chloroplasts, a damped binary oscillation as a function of flash number was observed in the kinetics of the decay of the fluorescence yield. The decay was faster on odd than on even-numbered flashes. 2. In the presence of low concentrations of 1,4-benzoquinone, the oscillation was more marked, and over the range approx 200--350 mV, independent of redox potential. The decay following flash 1 under these conditions had a half-time of approx. 200--400 microseconds. The decay following flash 2 was decelerated; the initial rate was up to 10-fold slower than after flash 1. 3. We suggest that the kinetics following a single flash reflect the rate of the reaction Q-B leads to QB-, and following the second flash, Q-B- leads to QB2-. Benzoquinone at low concentrations oxidises a residual fraction of B- which is usually reduced in the dark before the flash sequence. 4. A faster component in the decay (t u/2 approximately 140 microseconds) following the first flash titrated in over the range Eh greater than 350 mV. The binary oscillation was still apparent but delayed by one flash. 5. We discuss the relative redox potentials of the couples B/B- and B-/B2-, and the role of the component which titrates in at Eh greater than 350 mV.

Chloroplasts↗
PubMed1979

A high potential acceptor for photosystem II.

The effects of ferricyanide on Photosystem II reactions have been investigated by measurements of microsecond and millisecond prompt fluorescence and microsecond-delayed fluorescence in dark-adapted chloroplasts: (1) Titrations using ferri-ferrocyanide mixtures on: (a) the fast phase of the increase in fluorescence yield observed during a xenon flash, and (b) the normalised area above the millisecond fluorescence induction curve for chloroplasts inhibited by DCMU, showed a pH dependent mid point potential of 400 mV at pH 7.0 which varied by approx. -60 mV/pH unit between pH 6 and 8.5. (2) A saturating laser flash induced a fluorescence increase (as monitored by a weak measuring beam) of only 50% of that reached following a second flash in chloroplasts preincubated with ferricyanide and inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) prior to illumination. In the absence of ferricyanide, the fluorescence level reached after a single flash was initially close to that measured after a second flash (although the level subsequently declined). (3) The initial amplitude of the microsecond-delayed fluorescence excited by a single laser flash was diminished in chloroplasts dark-adapted with ferricyanide. In the presence of DCMU and ferricyanide, the amplitude was also diminished for the first flash of a series, but subsequently enhanced above the level obtained in chloroplasts in the presence of DCMU alone. (4) The above effects were not seen if DCMU was added to the chloroplasts before ferricyanide, or if the period of incubation with ferricyanide was much less than 4 min. (5) These results suggested the presence of a second acceptor Q2, with Em7 = 400 mV and n = 1, before the DCMU block in Photosystem II. There is 0.35--1 equivalent of the acceptor per reaction centre, and its reduction occurs within less than 5 mus. The role of the acceptor in double turnovers of the photochemistry during a single flash and its likely operating redox potential are discussed.

Chloroplasts↗
PubMed1979

Effects of pH on reactions on the donor side of photosystem II.

The effects of pH on the increase of fluorescence yield measured in the microsecond range, and on the microsecond delayed fluorescence have been studied in dark adapted chloroplasts as a function of flash number. (1) At pH 7, the amplitude of the fast-phase of the microsecond fluorescence yield rise oscillated as a function of flash number with period 4 and with maxima on flashes 1 and 5, and minima on flashes 3 and 7. The damped oscillations were apparent over the range between 6 and 8, although the absolute amplitude of the fast phase was diminished at the lower end of the range. At pH 4, there was no fast phase in the rise and, at pH 9, an enhanced fast-phase occurred only for the first flash. (2) The decay of microsecond delayed fluorescence was described by the sum of exponentials with half-times of 10--15 mus and 40--50 mus. Over the pH range 6- less than 8, the extrapolated initial amplitude and the proportion of the change due to the faster component showed oscillations which were opposite in phase to those observed for the prompt fluorescence yield rise; the slower component showed weaker oscillations of the same phase. At pH 4, there were no oscillations and the slow phase predominated. At pH 9, the delayed fluorescence intensity was diminished on the first flash, and high on subsequent flashes. (3) The results are interpreted in terms of a model in which protons are released during all transitions of the S-states with the exception of S1 leads to S2, and in which ther are two sites of inhibition on the donor side of the photo-system at extreme pH values. At pH 4, electron donation to P+ occurs with a half-time approx. 135 mus, either by a back reaction from Q-, or from D; electron transport is interrupted between Z1 and P. At pH 9, electron transport is inhibited between Z1 and Z2; rapid re-reduction of P+ by Z1 occurs after 1 flash, and on subsequent flashes electrons from D, an alternative donor reduce P+. The location of the positive charge on states S2 and S3 is discussed.

Chloroplasts↗
PubMed1974

Purification and some properties of bacteriophage ST-1.

Bacteriophage ST-1 is shown to be a small, isometric, single-stranded deoxyribonucleic acid (SS-DNA) virus with a diameter of about 260 nm. Standard methods for growth, assay, preparation of high-titer lysates, and purification of the phage are suggested. ST-1 infects K-12 and not C strains of Escherichia coli and requires a divalent cation to adsorb to susceptible bacteria. Adsorption also requires an activation of the particle brought on by incubation at 37 C. The latent and eclipse periods are essentially identical (9 to 11 min) in ST-1 infections, with an average burst size about 250 phages per cell. Multiple densities of ST-1 infectivity are observed during purification in CsCl gradients. The virus recovered from different densities has the same sedimentation coefficient and, therefore, all phage containing fractions are pooled during purification. The purified ST-1 particle has a sedimentation coefficient of 121S relative to phiX-174 (114S) in a sucrose gradient and a molecular weight of 6.8 x 10(6) (as estimated from its relative sedimentation). The nucleic acid is assumed to be SS-DNA on the basis of (i) the specific incorporation of (3)H-thymine, (ii) the dependence of its UV absorption on temperature, and (iii) its reaction with formaldehyde. ST-1 SS-DNA sediments at 24.4S relative to phiX-174 SS-DNA (23.8S).

Adenine↗