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Biomedical subjects

D Alexander

Publications and source records attributed to D Alexander.

At least 109 records · Page 6Linked to original sources
PubMed1989

Dephosphorylation of the human T lymphocyte CD3 antigen.

Previous studies demonstrated that activation of T lymphocytes by phorbol ester or mitogenic lectin leads to phosphorylation of Ser 126 of the CD3 antigen gamma chain, whereas treatment with ionomycin results in phosphorylation of both Ser 123 and 126 [Davies, A. A. et al. (1987) J. Biol. Chem. 262, 10918-10921]. In the present study, the dephosphorylation of Ser 123 and Ser 126 of the gamma chain was investigated. Phorbol-ester-induced phosphorylation of the gamma-chain Ser 126 in vivo was reversed following removal of phorbol ester. Dephosphorylation of both Ser 123 and 126 was also observed in vitro using the microsome fraction of T lymphocytes. In order to identify the phosphatases acting at these two sites, the immunoprecipitated gamma chain was used as substrate either following treatment with protein kinase C in vitro, in which case phosphorylation occurs mainly at Ser 123, or following in vivo phosphorylation of Ser 126. Purified oligomeric forms of the polycation-stimulated phosphatases were more effective in dephosphorylating both phosphorylated forms of the gamma chain compared with equivalent amounts of ATP,Mg2+-dependent phosphatases or calcineurin. By using phosphopeptide analogues of the CD3 gamma chain containing Ser 123 or Ser 126 as substrates (A3 and A6), it was shown that polycation-stimulated phosphatases selectively dephosphorylated Ser 123 compared to Ser 126. In order to determine which phosphatases dephosphorylate the gamma chain in microsomes, A3 and A6 were used as substrates for characterising phosphatases in microsomes from human T leukaemia Jurkat 6 cells. Three phosphopeptide phosphatases (250-400 kDa) co-eluted through five purification steps with three forms of polycation-stimulated phosphorylase phosphatase. The partially purified A3/A6 phosphopeptide phosphatases were insensitive to Ca2+, calmodulin and inhibitor-1, and dephosphorylated A3 preferentially compared with A6. A latent form of microsomal ATP,Mg2+-dependent phosphorylase phosphatase was stimulated 10-fold by trypsinisation, but did not dephosphorylate phosphopeptides A3 and A6. The results show that high-Mr forms of polycation-stimulated phosphatases are the only enzymes in human T leukaemia cell microsomes which dephosphorylate gamma chain phosphopeptides. The data point to an important role for polycation-stimulated phosphatases in regulating the phosphorylation state, and so function(s), of the CD3 antigen.

Amino Acid Sequence↗
PubMed1988

Levobunolol and betaxolol. A double-masked controlled comparison of efficacy and safety in patients with elevated intraocular pressure.

In a double-masked, randomized, controlled clinical trial, the authors evaluated the ocular hypotensive efficacy of twice-daily treatment with levobunolol (0.25 and 0.5%) and betaxolol (0.5%) in 85 patients with open-angle glaucoma or ocular hypertension. During the 3-month study, intraocular pressure (IOP) reductions in the two levobunolol groups were significantly greater than in the betaxolol group. From a mean baseline IOP of approximately 25 mmHg, overall mean reductions were 6.2 and 6.0 mmHg for the 0.25 and 0.5% levobunolol groups, respectively, and 3.7 mmHg for the betaxolol group. No clinically or statistically significant among-group differences were noted in the systemic safety variables evaluated. These data suggest that although all three treatments are effective, levobunolol provides a greater reduction in IOP than betaxolol.

Betaxolol↗
PubMed1988

Distress and self-soothing bedtime behaviors in hospitalized children with non-rooming-in parents.

The nature of behaviors during sleep onset latency (SOL) at night bedtime was studied in a group of 40 hospitalized children ages 3 to 8 years whose parents did not room-in. Research questions were: (a) What is the nature of behaviors during sleep onset latency of young children whose parents do not room-in? and (b) How are these behaviors related to family structure, social status, age, gender, previous hospitalizations, and number of days hospitalized? Child subjects were observed using the Senders, Signals, and Receivers (SSR) computer-compatible system to measure SOL, distress, and self-soothing behaviors for 2-3 consecutive nights. The median falling asleep time was 26 minutes. Variations in SOL and self-soothing behaviors were not significantly related to family structure, social status, gender, age, length of hospitalization, night of hospitalization, or previous hospitalizations. Greater distress behaviors were, however, significantly related to children of two-parent families and those from middle social status.

Adaptation, Psychological↗
PubMed1988

Anxiety levels of rooming-in and non-rooming-in parents of young hospitalized children.

This study examined levels of anxiety in 50 parents who roomed in and 51 parents who did not room in with their hospitalized children. The Spielberger State-Trait Anxiety Inventory was used to measure parental anxiety at two specific times. Statistically significant correlations were found between parental anxiety and number of children at home, parental educational level, and family social status. Of clinical importance were findings that non-rooming-in parents reported higher anxiety than rooming-in parents at both testings.

Anxiety↗
PubMed1987

Bicycle-related injuries.

To obtain epidemiologic data and information on the probable causes and severity of bicycle-related injuries, we interviewed all patients with such trauma. Between April 1 and Oct 1, 1983, 520 children presented to the Emergency Department of The Children's Hospital of Philadelphia with trauma related to two-wheeled nonmotorized bicycles. The ages of the patients ranged from 1 to 18 years (mean, 8.7 years), and most (72%) were males. Most accidents (84%) occurred less than five blocks from home, and 49% occurred in the street. Thirty-six percent of the patients admitted to stunt riding or going too fast when the accident occurred, and 36% claimed there was a problem with the surface on which they were riding. The accidents occurred when a patient lost control of the bike (45%), a patient on a bicycle was hit by a car (17%), or a pedestrian was hit by a bicyclist (10%). Only three patients were wearing protective equipment at the time of the accident. Most (54%) had received no specific safety instructions about bicycling. The extremities were injured in 53% of the accidents, but head and neck injuries accounted for 31%. Six percent required hospital admission. Males and children over 12 years of age were more likely to have multiple injuries. Accidents that occurred in the street or involved cars were associated with a greater number of serious and multiple injuries. The infrequent use of protective equipment and minimal safety instructions received by the patients in this study suggest that many bicycle-related injuries are preventable. Education of parents and children is recommended to improve bicycle safety.

Accident Prevention↗
PubMed1987

Transient bilateral peroneal palsy in a painter's model.

Peripheral neuropathies caused by pressure are common. The most common causes are pressure of the ulnar nerve at the elbow and of the median nerve at the wrist. Pressure neuropathy of the peroneal nerve at the level of the fibular neck is a rare syndrome. The literature describes well-defined etiologies of that syndrome: external pressure, tumors, ganglion, or stretching of the limb. A case of bilateral peroneal palsy in a painter's model caused by prolonged sitting in a specific position is described. Review of the literature revealed no such case described previously.

Adult↗
PubMed1986

Heterozygosity for phosphodiester glycosidase deficiency: a novel human mutation of lysosomal enzyme processing.

We have carried out studies on the fibroblasts of III-3, a clinically normal Lebanese individual previously reported to have abnormally high plasma lysosomal enzyme levels. Mannose-6-phosphate (man-6-P) receptors in III-3 fibroblasts were found to be functioning normally, but the cells had only half normal levels of phosphodiester glycosidase activity. Pinocytosis of III-3 fibroblast secreted beta-hexosaminidase B (hex B) into Sandhoff disease fibroblasts was 18% of control, and the apparent KD for binding of III-3 hex B to man-6-P receptors was 3.7 X 10(-9) M compared to 1.25 X 10(-9) M for control enzyme. Hex B secreted by III-3 fibroblasts included an enzyme pool less electro-negative than control enzyme which had a very low affinity for man-6-P receptors and which did not bind to DEAE-Sephadex. Treatment of this abnormal hex B with exogenous placental phosphodiester glycosidase increased its binding to man-6-P receptors three-fold. Secretion rates of seven lysosomal enzymes from III-3 fibroblasts were, on average, twice as great as rates measured for two I-cell disease heterozygote fibroblast lines. The results suggest that III-3 fibroblasts are heterozygous for phosphodiester glycosidase deficiency. The possibility that an individual homozygous for this enzyme deficiency would develop I-cell disease is discussed.

Carrier Proteins↗
PubMed1986

Anxiety of non-rooming-in parents of hospitalized children.

This study examined levels of anxiety in 51 parents who did not room in with their young hospitalized children. The Spielberger State-Trait Inventory was used to measure parental anxiety twice, with a 3-day interval. Levels of anxiety were significantly higher in parents with a greater number of children at home, less education, and lower social status. Findings of clinical significance were: the longer the child's hospitalization the more anxious parents became, especially if there were children at home; hospitalization of a child was more stressful for fathers because they maintain lower trait anxiety than mothers; and as parental visits to their hospitalized child decreased, parental anxiety levels increased.

Adult↗
PubMed1986

Cauda equina syndrome and lumbar disc herniation.

In a retrospective chart review of the cases of thirty-one patients with cauda equina syndrome secondary to a central disc lesion, we identified two modes of presentation. The first was an acute mode (ten patients) in which there were abrupt, more severe symptoms and signs and a slightly poorer prognosis after decompression, especially for the return of bladder function. The second mode of presentation (twenty-one patients) was a slower onset, characterized by prior symptoms for varying time-intervals before the more gradual onset of the cauda equina syndrome. All patients had urinary retention preoperatively. Bladder function was the most seriously affected function preoperatively and remained so postoperatively. The prognosis for return of motor function was good, since twenty-seven of the thirty patients who were operated on regained normal motor function. Preoperatively all patients had sciatica, which was bilateral in fourteen and unilateral in seventeen. The average time to surgical decompression after the patient was seen ranged from 1.1 days for the more acute lesions to 3.3 days for the second group. There was no correlation of these times with return of function. Therefore, even though early surgery is recommended, decompression does not have to be performed in less than six hours if recovery is to occur, as has been suggested in the past.

Adult↗
PubMed1985

Fructose-1,6-diphosphatase deficiency: diagnosis using leukocytes and detection of heterozygotes with radiochemical and spectrophotometric methods.

The first two cases of fructose-1,6-diphosphatase (FDPase) deficiency from the Middle East have been diagnosed on leukocytes using a spectrophotometric assay and a new radiochemical technique. The control mean for FDPase measured by the spectrophotometric assay was 178.2 nm mg-1 h-1 (n = 12), 66.8 nm mg-1 h-1 for obligate heterozygotes (n = 4) and non-detectable in the two patients. By the radiochemical assay the values were controls, 103.3; heterozygotes, 20.6; patients, 0.46 and 3.5 nm mg-1 h-1. Using both methods it was possible to identify two certain FDPase heterozygotes and three non-carriers in the family of one of the probands. The radiochemical method was found to be more effective in differentiating heterozygotes from controls than the spectrophotometric method. However, either technique may be conveniently used for the diagnosis of FDPase deficiency in leukocytes.

Adult↗
PubMed1985

Diabetes mellitus, thiamine-dependent megaloblastic anemia, and sensorineural deafness associated with deficient alpha-ketoglutarate dehydrogenase activity.

Three brothers with diabetes mellitus, thiamine-responsive megaloblastic anemia, and sensorineural deafness are reported. Two had, in addition, congenital septal defects. The activities of thiamine-dependent enzymes were determined in one patient, revealing low alpha-ketoglutarate dehydrogenase activity, which could have caused a sideroblastic anemia with secondary megaloblastic changes. The anemia was thiamine dependent. The cause of the diabetes mellitus was not known, but it was not type 1.

Adolescent↗