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Biomedical subjects

J K Roberts

Publications and source records attributed to J K Roberts.

At least 73 records · Page 4Linked to original sources
PubMed1988

Squamous cell carcinoma of the head and neck in patients 40 years of age and younger.

Squamous cell carcinoma of the head and neck is largely a disease of the middle-aged and elderly. When it occurs in younger patients, the prognosis for long-term survival appears to be worse than in the older age group. The records of 41 patients aged 40 years and younger who presented with squamous cell carcinoma of the head and neck were reviewed. Twenty-eight of these patients (68%) developed recurrence; of these, 21 (51%) died with disease, and two are alive with disease. These results indicate a trend toward poorer survival than previous rates reported nationally for all patients with carcinoma of the head and neck over a similar time period. Lesions of the oral tongue, nasopharynx, and paranasal sinuses seem to have a particularly poor prognosis.

Adult↗
PubMed1987

Laryngotracheal reconstruction. Sternohyoid myocutaneous rotary door flap.

The vascularized sternohyoid myocutaneous rotary door flap has been used for laryngotracheal reconstruction in ten patients in the past two years. Nine were reconstructed for laryngotracheal stenosis and one for immediate reconstruction after conservation laryngeal surgery for carcinoma. Before reconstruction, the nine patients with stenosis had each undergone a mean of eight surgical attempts at correction. Eight patients were tracheostomy dependent, and only two patients had effective voices. To date, seven patients have been decannulated and all ten have effective voices. No significant complications have been noted. This flap can provide a readily applicable, dependable technique that is useful in management of difficult laryngotracheal stenosis and for reconstruction after conservation laryngeal surgery.

Adult↗
PubMed1987

A vented laryngeal stent with phonatory and pressure relief capability.

This prototype vented laryngeal stent incorporates a dome-shaped, one-way valve that allows articulation of transmitted vibrations to produce speech, while preventing aspiration and not interfering with deglutition. The stent is placed endoscopically and is used in conjunction with a T-tube or a tracheostomy tube. The stent has been placed in seven patients for chronic aspiration, after partial laryngectomy, and with laryngotracheal reconstruction for stenosis. Aspiration pneumonia has not been seen in any patient after placement of the appropriate stent, with follow-up of 2 to 6 months. One patient's swallowing improved and none deteriorated. All patients were able to phonate with the stent in place. No significant long-term sequelae are apparent in three patients whose stents were removed after resolution of their primary diseases.

Adult↗
PubMed1986

Neuropsychiatric complications of mental retardation.

Certain aspects of mental retardation and organic brain disease are discussed: notably, psychopathology, the delayed effects of congenital infections, epilepsy, and the association between Down's syndrome and dementia.

Brain Diseases↗
PubMed1985

Relationships between the rate of synthesis of ATP and the concentrations of reactants and products of ATP hydrolysis in maize root tips, determined by 31P nuclear magnetic resonance.

Using 31P NMR spectroscopy, we have measured the rate of ATP synthesis, and the free concentrations of ATP, ADP, cytoplasmic Pi, and H+ in maize root tips under a wide range of conditions. We show that the ratio [ATP]/[ADP] in normoxic root tips is greater than 25. We found no simple relationship between the concentration of ATP and the rate of ATP synthesis: when the rate of ATP synthesis decreases in response to different treatments, the concentration of ATP can increase, decrease, or remain unchanged. Clear relationships were obtained, however, when the rate of synthesis of ATP was plotted against the logarithm of the ratio psi, defined as [ATP]/[ADP][Pi][H+]. Two curves were obtained, depending on which of two situations pertained. First, if mitochondrial ATP synthesis was inhibited, e.g., by KCN or hypoxia, ln psi decreased monotonically as rates of ATP synthesis decreased. The decrease in ln psi may account for decreases in the rates of biosynthetic reactions dependent on ATP, such as protein synthesis, as they approach equilibrium. Second, if consumption of ATP for biosynthetic reactions was inhibited, by treatment with succinate, ln psi increased as rates of ATP synthesis decreased. The increase in ln psi may account for decreases in the rate of ATP synthesis, as oxidative phosphorylation approaches equilibrium.

Adenosine Diphosphate↗
PubMed1985

Further Evidence that Cytoplasmic Acidosis Is a Determinant of Flooding Intolerance in Plants.

We present two pieces of evidence that regulation of cytoplasmic pH near neutrality is a prerequisite for survival of root tips during hypoxia. First, blackeye peas and navy beans show earlier cytoplasmic acidosis under hypoxia than soybeans or pumpkin or maize, and die earlier. Second, when cytoplasmic acidosis in maize root tips is greatly retarded by treatment with 25 millimolar Ca(NO(3))(2), they remain viable under hypoxia for a much longer period of time than untreated hypoxic root tips. We also show that viability of maize root tips is unaffected by the supply of exogenous sugar (and so on the rate of ethanolic fermentation) for at least 16 hours of hypoxia.

Journal Article↗
PubMed1984

Mechanisms of cytoplasmic pH regulation in hypoxic maize root tips and its role in survival under hypoxia.

We show that a transient lactic fermentation provides the signal triggering ethanol production in hypoxic maize root tips. The signal is cytoplasmic pH. This interaction between lactic and ethanolic fermentation permits tight cytoplasmic pH regulation during hypoxia--cytoplasmic pH remaining near neutrality for several hours. Mutant roots unable to synthesize ethanol can neither regulate cytoplasmic pH nor maintain ATP levels during extended periods of hypoxia and, like vertebrate tissues, are less tolerant of hypoxia than normal maize. This indicates that cytoplasmic pH regulation is an important factor in survival under hypoxia.

Cytoplasm↗
PubMed1984

Cytoplasmic acidosis as a determinant of flooding intolerance in plants.

We present evidence that cytoplasmic acidosis is a cause of meristematic death in hypoxic root tips of maize and pea seedlings. Usually, leakage of acid from the vacuole is responsible for cytoplasmic acidosis. Leakage of acid, which occurs earlier during hypoxia in pea root tips than in maize root tips, appears to account for the lower tolerance of peas for hypoxia. Cytoplasmic acidosis is accelerated in maize root tips that are either (i) deficient in alcohol dehydrogenase, so that lactic acid production continues throughout hypoxia, or (ii) exposed to external CO2 during hypoxia, or (iii) perfused slowly so that escape of CO2 produced during ethanolic fermentation is retarded. All three conditions decrease the length of time maize root tips can tolerate hypoxia; more rapid cytoplasmic acidosis is associated with more rapid death under hypoxia. Possible mechanisms by which cytoplasmic acidosis leads to death are suggested; the mechanism does not involve inhibition of glycolysis by low pH.

Anaerobiosis↗
PubMed1984

Acquisition of Thermotolerance in Soybean Seedlings : Synthesis and Accumulation of Heat Shock Proteins and their Cellular Localization.

When soybean Glycine max var Wayne seedlings are shifted from a normal growth temperature of 28 degrees C up to 40 degrees C (heat shock or HS), there is a dramatic change in protein synthesis. A new set of proteins known as heat shock proteins (HSPs) is produced and normal protein synthesis is greatly reduced. A brief 10-minute exposure to 45 degrees C followed by incubation at 28 degrees C also results in the synthesis of HSPs. Prolonged incubation (e.g. 1-2 hours) at 45 degrees C results in greatly impaired protein synthesis and seedling death. However, a pretreatment at 40 degrees C or a brief (10-minute) pulse treatment at 45 degrees C followed by a 28 degrees C incubation provide protection (thermal tolerance) to a subsequent exposure at 45 degrees C. Maximum thermoprotection is achieved by a 2-hour 40 degrees C pretreatment or after 2 hours at 28 degrees C with a prior 10-minute 45 degrees C exposure. Arsenite treatment (50 micromolar for 3 hours) also induces the synthesis of HSP-like proteins, and also provides thermoprotection to a 45 degrees C HS; thus, there is a strong positive correlation between the accumulation of HSPs and the acquisition of thermal tolerance under a range of conditions.During 40 degrees C HS, some HSPs become localized and stably associated with purified organelle fractions (e.g. nuclei, mitochondria, and ribosomes) while others do not. A chase at 28 degrees C results in the gradual loss over a 4-hour period of the HSPs from the organelle fractions, but the HSPs remain selectively localized during a 40 degrees C chase period. If the seedlings are subjected to a second HS after a 28 degrees C chase, the HSPs rapidly (complete within 15 minute) relocalize in the organelle fractions. The relative amount of the HSPs which relocalize during a second HS increases with higher temperatures from 40 degrees C to 45 degrees C. Proteins induced by arsenite treatment are not selectively localized with organelle fractions at 28 degrees C but become organelle-associated during a subsequent HS at 40 degrees C.

Journal Article↗
PubMed1984

Measurement of mitochondrial ATPase activity in maize root tips by saturation transfer p nuclear magnetic resonance.

We show that saturation transfer (31)P nuclear magnetic resonance can be used to measure the activity of the mitochondrial ATPase of maize (Zea mays L. hybrid WW x Br38) root tips in vivo. Unidirectional rates of ATP synthesis were determined in the steady state (i.e. ATP and cytoplasmic orthophosphate constant) under various conditions. These measurements, and determinations of oxygen consumption, give a P/O ratio (measured in the living tissue) close to 3. In succinate-fed root tips the P/O ratio is approximately 2. Cyanide inhibits the rate of ATP synthesis by two-thirds (P/O ratio approximately 1), with an effective inhibitor constant of approximately 35 micromolars. We show that the alternative electron pathway cannot make ATP, and does not normally operate in this tissue. This method of studying plant mitochondrial metabolism avoids potential artifacts encountered in studies using isolated and purified mitochondria. The method also allows, for the first time, direct and simultaneous examination of the relationship between the rate of ATP synthesis and levels of metabolites such as ATP, and derived parameters such as phosphorylation potential.

Journal Article↗
PubMed1984

Salt stimulation of phosphate uptake in maize root tips studied by p nuclear magnetic resonance.

The effects of external salt and inorganic phosphate (Pi) on the concentrations of vacuolar Pi, and cytoplasmic Pi, ATP, glucose-6-phosphate and UDP-glucose in maize root tips were examined using (31)P nuclear magnetic resonance spectroscopy. We observed a more than two-fold stimulation of Pi uptake from 10 millimolar KH(2)PO(4) solutions when root tips were exposed to 100 millimolar NaCl + CaCl(2). This stimulation of Pi uptake was associated with an increase in the concentration of cytoplasmic Pi in root tip cells. Thus, the molar ratio of cytoplasmic Pi to Pi + ATP + glucose-6-phosphate + UDP-glucose increased greatly in root tips exposed to salt and Pi. We speculate that it is this disturbance in relative concentrations of cytoplasmic phosphates (which we show are normally tightly regulated) that is responsible for both the greater rate of uptake of Pi by vacuoles of excised maize root tips, and the previously documented stimulation of Pi translocation from root to shoot in whole maize plants exposed to salt and Pi.

Journal Article↗
PubMed1984

The use of the C.A.T. head scanner in clinical psychiatry.

Three hundred and twenty-three patients were referred by psychiatrists for scanning with a 160 X 160 matrix CT 1010 Head Scanner at the Maudsley Hospital during the first year this machine was in use (1977/1978). Two hundred and one referrals were for clinical and 122 for research reasons, 50% of the former and 57% of the latter showed some abnormality on their scans. Review of the patients' notes identified data that were significantly predictive of abnormal scan results; and the referring psychiatrists were significantly more able to predict the scan results correctly during the second six months of the study. Diagnosis, management, and/or prognosis were influenced in 11.7% of those patients scanned for clinical reasons.

Adult↗
PubMed1983

Schizophrenic psychosis associated with aqueduct stenosis in adults.

The case histories of five adult patients with hydrocephalus and aqueduct stenosis are presented. All the cases were associated with prominent psychotic symptoms (delusions, hallucinations or thought disorder). In the three cases where operative intervention was carried out the diagnosis was made in adult life. Using the Present State Examination all five cases were classified as having schizophrenic psychosis. The possible reasons for this association are discussed.

Adolescent↗
PubMed1982

Regulation of Cytoplasmic and Vacuolar pH in Maize Root Tips under Different Experimental Conditions.

(31)P-Nuclear magnetic resonance spectra of perfused maize (Zea mays L., hybrid WW x Br 38) root tips, obtained at 10-minute intervals over 12 hours or longer, indicate that no cytoplasmic or vacuolar pH changes occur in these cells in the presence of 25 millimolar K(2)SO(4), which induces extrusion of 4 to 5 microequivalents H(+) per gram per hour. In contrast, hypoxia causes cytoplasmic acidification (0.3-0.6 pH unit) without a detectable change in vacuolar pH. The cytoplasm quickly returns to its original pH on reoxygenation. Dilute NH(4)OH increases the vacuolar pH more than it does the cytoplasmic pH; after NH(4)OH is removed, the vacuole recovers its original pH more slowly than does the cytoplasm. The results indicate that regulation of cytoplasmic pH and that of vacuolar pH in plant cells are separate processes.

Journal Article↗
PubMed1982

The lateralising significance of hypergraphia in temporal lobe epilepsy.

Six patients with hypergraphia and epilepsy are presented and their clinical features compared with other patients reported in the literature. It is suggested that hypergraphia occurs more frequently in patients with right-sided non-dominant temporal lobe lesions, in contrast for example to the schizophreniform presentation of left-sided lesions. Other features of psychopathology possibly associated with non-dominant lesions, including elation, hypereligiosity and déjà vu experiences, are also discussed.

Adult↗