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L Patel

Publications and source records attributed to L Patel.

At least 55 records · Page 3Linked to original sources
PubMed1996

Comparison of the segregation of the RYR1 C1840T mutation with segregation of the caffeine/halothane contracture test results for malignant hyperthermia susceptibility in a large Manitoba Mennonite family.

BACKGROUND: Malignant hyperthermia (MH) is an important cause of anesthesia-induced death. Malignant hyperthermia susceptibility is diagnosed using the in vitro caffeine/halothane contracture test (CHCT) in fresh muscle biopsy specimens. The CHCT test is highly invasive, expensive, and lacks 100% specificity. Genetic and biochemical evidence provide strong support for the view that the substitution of cysteine for arginine 614 (Arg614Cys) in the human ryanodine receptor gene is one of several mutations that are likely to cause human MH. DNA testing was compared with CHCT as a means of predicting MH susceptibility in a large MH family in which the Arg614Cys mutation was detected. METHODS: A comparison of CHCT and DNA-based diagnosis was conducted in a large Manitoba Mennonite MH kindred identified by an index patient who died at age 45 yr of an MH crisis after general anesthesia. The presence of the Arg614Cys mutation was detected through a combination of polymerase chain reaction and restriction endonuclease digestion. Blood samples for DNA analysis were obtained from 68 family members, including 19 who had undergone muscle biopsies and 1 who had a documented crisis but did not undergo biopsy. Family members were classified as MH-susceptible or MH-normal on the basis of the CHCT. RESULTS: Twenty-two persons were found to be heterozygous for the Arg614Cys mutation. Five of these persons had prior positive CHCT results and one had an MH crisis but did not undergo biopsy. On DNA testing, 44 persons were found to be homozygous for the normal allele. Of these, ten had been classified as MH-normal and five as MH-susceptible on the basis of the CHCT. On reevaluation of the data obtained in our earlier CHCT diagnoses, we found that the condition of the muscle was poor, with no twitch, for three of five individuals homozygous for the normal allele but originally classified as MH-susceptible and for one who was homozygous for the normal allele and originally classified as MH-normal. Caffeine/halothane contracture test results for these four persons were considered invalid. The twitch response was good for the two remaining persons who were homozygous for the normal allele but classified as MH- susceptible, because contracture was observed with appropriately low levels of both caffeine and halothane. CONCLUSIONS: An absolute correlation between DNA test results and CHCT assignment could not be made in this kindred. Possible explanations for discordance are that the Arg614Cys mutation is not linked to MH, that a second MH mutation is segregating in the family, or that there are errors in the CHCT. Because there is strong evidence supporting the causal nature of the Arg614Cys mutation, the discordant persons are not closely related within the pedigree as they would be if a second MH mutation were segregating, and the CHCT is not 100% accurate, we propose that the observed discordance between DNA test results and CHCT assignment in this kindred results from two false-positive diagnoses by the CHCT.

Anesthetics, Inhalation↗
PubMed1996

Early repair of inguinal hernia in preterm infants with oxygen-dependent bronchopulmonary dysplasia.

Despite inguinal hernia being both common and problematic in a significant proportion of preterm infants with bronchopulmonary dysplasia (BPD), there has been a reluctance to intervene surgically for fear of exacerbating the underlying lung disease. We report our experience of early operation in 12 consecutive infants with varying degrees of oxygen-dependent BPD and investigate the effect of general anaesthesia and herniotomy on pulmonary function by measuring oxygen requirements prior to and following operation. Two infants who required oxygen in a concentration in excess of 95% failed to improve and died from the pulmonary disease 6 and 8 weeks following their operation. The remaining infants all showed a reduction in mean oxygen requirements in the weeks following operation. We conclude that, in the short term, hernia repair performed under general anaesthesia in infants with BPD of varying severity had no adverse effects on respiratory function, as determined by oxygen requirements. We suggest that in certain infants early repair may have been beneficial--potential mechanisms are explored.

Birth Weight↗
PubMed1995

Use of fluorescence resonance energy transfer to estimate intramolecular distances in the Msx-1 homeodomain.

We have utilized fluorescence resonance energy transfer (FRET) to investigate the spatial proximities of segments in the Msx-1 homeodomain (Msx). This strategy makes use of a single, invariant tryptophan (Trp-48) in helix III as the donor for FRET. The acceptor molecule, 5-[[[(iodoacetyl)amino]-ethyl]amino]naphthalene-1-sulfonic acid (AEDANS), was incorporated into Msx at positions 6, 10, or 27 which are within the N-terminal arm, and helices I and II since these segments have been implicated in interactions with helix III. Specific incorporation of AEDANS was achieved by using a two-step strategy consisting of site-directed mutagenesis for introducing unique cysteine residues at the selected positions followed by covalent modification of these cysteine residues with AEDANS. Using this approach, we demonstrated energy transfer between Trp-48 and the AEDANS-labeled cysteines at positions 6, 10, and 27 and estimated the distances between the Trp-48 and AEDANS pairs to be 19, 23, and 16 A, respectively. We further demonstrated that FRET provides a strategy for detecting subtle alterations in protein conformation that result from replacement of specific residues in helix III and the N-terminal arm. Together, these findings show that FRET provides a useful approach for estimating intramolecular distances and for examining the conformation of Msx. Moreover, given the fact that Trp-48 is invariant among all homeodomain sequences, we propose that FRET will provide a general approach for facilitating comparative analyses of homeodomain conformations.

Amino Acid Sequence↗
PubMed1995

Adrenal function following topical steroid treatment in children with atopic dermatitis.

Adrenal suppression is a potential complication of topical corticosteroid treatment in atopic dermatitis. We used a low-dose adrenocorticotrophic hormone (ACTH) test (500 ng/1.73 m2) to detect subtle changes in adrenal glucocorticoid function in 14 prepubertal children with moderate or severe atopic dermatitis affecting 16-90% (median 58%) of the body surface area. All had received regular treatment with mild potency BNF (British National Formulary) classification topical corticosteroid ointments (hydrocortisone 48.7-223.2 mg/m2 body surface area/day; median 134.2) for 3-10 years (median 6.5 years). Nine children had also intermittently used moderate potency preparations. However, none had been treated with corticosteroids by any other route in the preceding 6 months. Fourteen prepubertal children with constitutional short stature, without atopic disease, served as controls. The basal, peak, increment and area-under-curve in plasma cortisol concentrations in children with atopic dermatitis were not significantly different from controls, indicating normal adrenal sensitivity to low-dose ACTH. However, the peak in plasma cortisol occurred earlier in children with atopic dermatitis (median 17.5 min) than in controls (median 25 min) (P = 0.02). In addition, there was a significant inverse relationship between time to peak and extent of atopic dermatitis (rs = -0.52; P < 0.05), but not topical steroid treatment dose or score in children with atopic dermatitis. These findings indicate accelerated adrenal responsiveness to ACTH in children with atopic dermatitis, which is independent of treatment. Mild to moderately potent topical corticosteroid ointments in these doses did not suppress adrenal glucocorticoid function in this sample of children with atopic dermatitis.

Administration, Topical↗
PubMed1995

Increasing dose regimen in children with reactions to ceftazidime.

BACKGROUND: Of 87 consecutive patients with cystic fibrosis treated with 859 courses of intravenous ceftazidime, 15 patients experienced reactions to drugs. OBJECTIVE: To see if by varying the means of administration further courses of treatment with ceftazidime could be tolerated in subjects who had experienced drug reactions. METHODS: Starting with a dose of 1 mg per hour, and doubling the dose every hour, ceftazidime was administered at increasing dosage by continuous infusion, reaching a rate of 150-300 mg/kg/day. Thereafter the full daily dose was given in three divided bolus doses. For patients who tolerated the maximum infusion rate but reacted adversely to bolus doses, the procedure was restarted, and once the normal daily dose rate had been achieved, treatment was completed by continuous intravenous infusion rather than bolus doses. RESULTS: Of the 15 patients, three patients with urticaria and four patients with nonurticarial itchy rash tolerated further courses of ceftazidime without adverse reactions, and two patients have not had further treatment with intravenous antibiotics. The increasing dose regimen was tolerated in five of the remaining six patients, and further courses of treatment were tolerated in the four patients in whom this was required. One patient had recurrent urticaria despite three attempts at using the regimen, and treatment was given with alternative antibiotics. CONCLUSION: A continuous drug infusion regimen of starting at a very low dosage and then increasing the dosage offers the potential for further treatment in some children with cystic fibrosis with adverse reactions to ceftazidime.

Adolescent↗
PubMed1994

Design of a "minimAl" homeodomain: the N-terminal arm modulates DNA binding affinity and stabilizes homeodomain structure.

This report investigates the sequence specificity requirements for homeodomain structure and DNA binding activity by the design and synthesis of a "minimAl" homeodomain (for minimalist design and alanine scanning mutagenesis) which contains the consensus residues and in which all nonconsensus residues have been replaced with alanine. The murine homeodomain Msx served as the prototype for the minimAl homeodomain, Ala-Msx. We show that Ala-Msx binds to DNA specifically, albeit with lower affinity than Msx. A derivative of the minimAl homeodomain, Ala-Msx(NT), which contains a native rather than an alanine-substituted N-terminal arm, has similar DNA binding affinity as Msx. We show that the native N-terminal arm stabilizes the tertiary structure of the minimAl homeodomain. Although Ala-Msx resembles a molten-globule protein, the structure of Ala-Msx(NT) is similar to Msx. The requirement for an intact N-terminal arm is not unique to the minimAl homeodomain, since the N-terminal arm also promotes high-affinity binding activity and appropriate tertiary structure of Msx. Therefore, the homeodomain "scaffold" consists of consensus residues, which are sufficient for DNA recognition, and nonconsensus residues in the N-terminal arm, which are required for optimal DNA binding affinity and appropriate tertiary structure. MinimAl design provides a powerful strategy to probe homeodomain structure and function. This approach should be of general utility to study the sequence specificity requirements for structure and function of other DNA-binding domains.

Alanine↗
PubMed1994

Eosinophilia in newborn infants.

To evaluate the clinical significance of eosinophilia in newborn infants, 261 admissions to the neonatal unit over a 12-month period were studied retrospectively; 33 babies with eosinophilia (> 1.0 x 10(9)/l) were studied. Clinical and laboratory data for the first month of life were compared, where available, between gestational age-matched pairs with and without eosinophilia. Of the 33 babies with eosinophilia, 23 were > 26 weeks' gestation and all had age-matched controls; 10 were < or = 26 weeks' gestation but had no appropriate gestational age-matched controls. Babies > 26 weeks' gestation with eosinophilia had a significantly higher number of septic episodes than controls: 20 of 23 versus 4 of 23. All 10 babies < or = 26 weeks' gestation with eosinophilia developed sepsis. Infections with gram-negative organisms and necrotizing enterocolitis occurred only in babies who developed eosinophilia. In 5 babies no cause for the eosinophilia was found. In conclusion, eosinophilia in the newborn is usually explainable and is most often associated with infection.

Bacterial Infections↗
PubMed1994

The influence of body mass index on growth hormone secretion in normal and short statured children.

Obesity is one of the factors which limits the value of growth hormone (GH) provocation tests in the diagnosis of GH deficiency. We have therefore examined (1) the relationship between urinary GH (uGH), a physiological parameter of GH secretion, and percent ideal body mass index (BMI%), an indirect estimate of body fat, in 528 schoolchildren; and (2) the extent to which peak arginine stimulated (0.5 g/kg i.v.) GH concentrations were influenced by BMI% in 176 short normal (SN) children and 48 girls with Turner syndrome (TS). The mean BMI% (SD) for each group was 102.9 (10.8) in schoolboys, 102.7 (13.4) in schoolgirls, 95.8 (13.9) in SN boys, 98.2 (21.4) in SN girls and 105.9 (18.0) in TS. BMI% correlated inversely with log uGH in school-children (boys r = -0.16, P = 0.01; girls r = -0.25, P < 0.001). However, if each sex was subdivided by pubertal status, the inverse relationship only persisted in pubertal (boys r = -0.18, P = 0.04; girls r = -0.39, P < 0.001) but not prepubertal children (boys r = -0.1, P = 0.3; girls r = -0.11, P = 0.3). BMI% was also inversely related to log peak stimulated GH concentration in SN girls (r = -0.49, P < 0.001) but not SN boys (r = -0.14, P = 0.2) or girls with TS (r = 0.19, P = 0.2). The inverse relationship between normal body fat and physiological GH secretion becomes significant during puberty; in girls it accounts for 15% of the variability in uGH excretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1992

Site-directed mutagenesis of lysine 319 in the lactose permease of Escherichia coli.

Lys319, which is on the same face of putative helix X as His322 and Glu325 in the lactose permease of Escherichia coli, has been replaced with Leu by oligonucleotide-directed, site-specific mutagenesis. Although previous experiments suggested that the mutation does not alter permease activity, we report here that K319L permease is unable to catalyze active lactose accumulation or lactose efflux down a concentration gradient. The mutant does catalyze facilitated influx down a concentration gradient at a significant rate; however, the reaction occurs without concomitant H+ translocation. The mutant also catalyzes equilibrium exchange at about 50% of the wild-type rate, but it exhibits poor counterflow activity. Finally, flow dialysis and photoaffinity labeling experiments with p-nitrophenyl alpha-D-galactopyranoside indicate that K319L permease probably has a markedly decreased affinity for substrate. The alterations described are not due to diminished levels of the mutated protein in the membrane, since immunological studies reveal comparable amounts of permease in wild-type and K319L membranes. It is proposed that Lys319, like Arg302, His322, and Glu325, plays an important role in active lactose transport, as well as substrate recognition.

Affinity Labels↗
PubMed1992

Trophic action of local intraileal infusion of insulin-like growth factor I: polyamine dependence.

Experiments were performed to determine potential growth-promoting effects of human recombinant insulin-like growth factor I (hrIGF-I) in the gastrointestinal tract. IGF-I and IGF-II, but not insulin, were potent (half-maximal effective concentration 0.3 nM) and efficacious inducers of the growth-related enzyme ornithine decarboxylase (ODC) in the gut-derived cell line IEC-6. Maximal ODC induction was observed after treatment of cells with 10 nM IGF-I. In whole animal experiments, bolus intraileal injection of 10 nM hrIGF-I in anesthetized rats induced a 300% increase in ileal mucosal ODC activity, which was sensitive to inhibition with difluoromethylornithine (DFMO). Rats were implanted intraperitoneally with osmotic minipumps filled with 0.9% NaCl or 10 nM IGF-I that was delivered to the ileal lumen by a short Silastic catheter. Sixty-six hours of 1 microliter/h intraluminal IGF-I infusion produced an approximate doubling of mucosal wet weight (NaCl 50 mg vs. IGF-I 102 micrograms/2 cm mucosa) and total mucosal RNA, DNA, and protein content over that in rats that were infused with NaCl. Intraperitoneal treatment with 200 mg/kg DFMO three times per day had little effect on ileal mucosal mass, but completely inhibited the trophic response to IGF-I infusion. IGF-I infusion had no effect on body weight.

Animals↗
PubMed1991

Prostaglandin production in human endometrium following continuous exposure to low-dose levonorgestrel released from a vaginal ring.

Arachidonic acid metabolites produced by primary cultures of human endometrial cells derived from biopsies obtained before and after exposure to 20 micrograms/day levonorgestrel for 84 +/- 1 days were analysed by reverse phase HPLC. This revealed a significant increase in PGF1 alpha and an epoxide metabolite upon levonorgestrel stimulation. The proportion of epoxide metabolite, PGF1 alpha and PGE2 were positively correlated with serum levonorgestrel levels while HETES, PGE2 and epoxide were similarly correlated with serum oestradiol. The extent of intermenstrual bleeding during exposure to levonorgestrel was correlated with the proportion of epoxide and HETES products in vitro which is discussed in relation to their physiological function.

6-Ketoprostaglandin F1 alpha↗
PubMed1990

Altered protein conformation on DNA binding by Fos and Jun.

The protein products of the c-fos and c-jun proto-oncogenes (Fos and Jun, respectively) form a heterodimeric protein complex that interacts with the activator protein-1 (AP-1) binding site and regulates gene transcription in response to extracellular stimuli. Protein dimerization is mediated primarily by a coiled-coil-like structure termed the leucine-zipper and DNA binding occurs primarily through regions of each protein rich in basic amino acids that contact both strands of the AP-1 site. The precise nature of the protein-DNA interaction is unknown as studies concerned with dimerization and DNA binding by Fos and Jun have relied on indirect methods to investigate protein-protein-DNA interactions. Here we have developed assay systems using fluorescence spectroscopy and circular dichroism to monitor dimerization and DNA binding directly. The results indicate that the interaction of Fos and Jun with DNA results in an altered conformation of the protein dimers and an increased alpha-helical content. These techniques may have general application in studies concerning the interaction of transcriptional regulatory proteins with specific DNA target sequences.

Binding Sites↗
PubMed1990

Redox regulation of fos and jun DNA-binding activity in vitro.

The proto-oncogenes c-fos and c-jun function cooperatively as inducible transcription factors in signal transduction processes. Their protein products, Fos and Jun, form a heterodimeric complex that interacts with the DNA regulatory element known as the activator protein-1 (AP-1) binding site. Dimerization occurs via interaction between leucine zipper domains and serves to bring into proper juxtaposition a region in each protein that is rich in basic amino acids and that forms a DNA-binding domain. DNA binding of the Fos-Jun heterodimer was modulated by reduction-oxidation (redox) of a single conserved cysteine residue in the DNA-binding domains of the two proteins. Furthermore, a nuclear protein was identified that reduced Fos and Jun and stimulated DNA-binding activity in vitro. These results suggest that transcriptional activity mediated by AP-1 binding factors may be regulated by a redox mechanism.

Amino Acid Sequence↗
PubMed1990

Mechanisms of parturition: the transfer of prostaglandin E2 and 5-hydroxyeicosatetraenoic acid across fetal membranes.

Prostaglandin E2 production by amnion is thought to be an important event in the onset of human labor. It has been suggested that 5-hydroxyeicosatetraenoic acid, also produced in the amnion, may mediate prelabor contractions. For either of these compounds to play a paracrine role they need to cross the chorion, which has a high capacity to metabolize prostaglandins. With the use of an in vitro system we have shown that both prostaglandin E2 and 5-hydroxyeicosatetraenoic acid cross either amnion or intact amnion-chorion-decidua at a rate similar to that of an extracellular marker sucrose. Analysis by high performance liquid chromatography revealed that at physiologic concentrations neither prostaglandin E2 nor 5-hydroxyeicosatetraenoic acid were metabolized by amnion alone. Moreover, 100% of the 5-hydroxyeicosatetraenoic acid and 72% of the prostaglandin E2 remained in the active form after passage across intact amnion-chorion-decidua. There did not appear to be any difference in the rate of transfer or permeability of the membranes before or after spontaneous labor. We conclude that both 5-hydroxyeicosatetraenoic acid and prostaglandin E2 synthesised in the amnion can cross the membranes by diffusion through the extracellular space, remaining largely unmetabolized, and may play a role in the onset of human labor.

Biological Transport↗