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Biomedical subjects

J King

Publications and source records attributed to J King.

At least 19 recordsLinked to original sources
PubMed1992

Amino acid substitutions influencing intracellular protein folding pathways.

Though an increasing variety of chaperonins are emerging as important factors in directing polypeptide chain folding off the ribosome, the primary amino acid sequence remains the major determinant of final conformation. The ability to identify cytoplasmic folding intermediates in the formation of the tailspike endorhamnosidase of phage P22 has made it possible to isolate two classes of mutations influencing folding intermediates-temperature-sensitive folding mutations and global suppressors of tsf mutants. These and related amino acid substitutions in eukaryotic proteins are discussed in the context of inclusion body formation and problems in the recovery of correctly folded proteins.

Amino Acid Sequence↗
PubMed1992

The effects of nicotine plus haloperidol compared to nicotine only and placebo nicotine only in reducing tic severity and frequency in Tourette's disorder.

We studied the effects of chewing nicotine gum on tic frequency and severity in 10 patients with Tourette's disorder (TD) on haloperidol, versus 9 untreated TD patients; placebo gum was administered to 5 of these untreated patients. Videotapes of patients during a 2-hr period of 30 min baseline, 30 min gum chewing, and two 30-min postgum-chewing periods were utilized. For those TD patients on haloperidol, significant reductions occurred in tic frequency and severity during the gum-chewing and the two postgum-chewing periods. Nicotine gum alone caused a decrease in tic frequency only during gum-chewing and one postgum-chewing period, while placebo gum showed no effect. In this study, nicotine markedly potentiated haloperidol effects in treating TD, and showed lesser effects on TD when used alone.

Adolescent↗
PubMed1992

An unstable triplet repeat in a gene related to myotonic muscular dystrophy.

Synthetic oligonucleotides containing GC-rich triplet sequences were used in a scanning strategy to identify unstable genetic sequences at the myotonic dystrophy (DM) locus. A highly polymorphic GCT repeat was identified and found to be unstable, with an increased number of repeats occurring in DM patients. In the case of severe congenital DM, the paternal triplet allele was inherited unaltered while the maternal, DM-associated allele was unstable. These studies suggest that the mutational mechanism leading to DM is triplet amplification, similar to that occurring in the fragile X syndrome. The triplet repeat sequence is within a gene (to be referred to as myotonin-protein kinase), which has a sequence similar to protein kinases.

Amino Acid Sequence↗
PubMed1992

Folding and assembly of oligomeric proteins in Escherichia coli.

High levels of expression of oligomeric proteins in heterologous systems are frequently associated with misfolding and accumulation of the polypeptides in inclusion bodies. This reflects aspects of the folding and assembly pathways of oligomeric proteins, which generally proceed from either folding intermediates or native-like metastable species that are not in their final conformation. Methods for optimizing the yield of correctly assembled oligomers are discussed.

Amino Acid Sequence↗
PubMed1992

The concept of lymph node dissections in patients with malignant melanoma.

Therapeutic lymph node dissections in patients with grossly palpable metastatic melanoma are performed to control regional disease, to salvage a small percentage of patients, and to obtain staging information. Patients with malignant melanoma may undergo elective lymph node dissections, when the basin is clinically negative, for three reasons. There is some evidence based on large retrospective studies that survival is increased in patients with intermediate thickness melanoma if elective lymph node dissections are performed as part of the initial treatment of the primary melanoma. Second, in a small percentage of patients, a previous elective lymph node dissection may have helped control disease in the regional lymphatics, so that more extensive procedures, including amputations, are not necessary. Another important reason is to obtain staging and prognostic information for the patient because most adjuvant protocols are based on the presence or absence of disease in the regional basin. During a 3-year period, 115 patients have undergone a regional nodal dissection at the Moffitt Cancer Center and James Haley VA Hospital as part of their surgical treatment. With a follow-up of 3 years, patients with 1 node positive do significantly better than those with more than 1 node positive in their dissection (p = 0.06). The percentage of nodes positive is also important. Those patients who have less than 10% of their nodes involved with metastatic melanoma have a better survival than those patients whose percentage is greater than 10% (p = 0.07).

Adolescent↗
PubMed1992

A trial of health education aimed to reduce cigarette smoking among pregnant women.

Three hundred and forty-six women who reported smoking one or more cigarettes per day prior to the 20th week of gestation were recruited into a trial of health educational counselling to stop or reduce cigarette smoking. Counselling was begun at the first prenatal visit and then continued subsequently in the home. Among the 319 women included in analysis, at first follow-up visit those who received counselling smoked 1.7 fewer cigarettes a day than control women (P less than 0.05) and 10.4% had stopped smoking, compared to 5.4% in the control group (NS). Similar but not significant differences were noted at the end of pregnancy. Study effects were limited to the 284 women smoking five or more cigarettes a day at booking. This report refers primarily to them. At first follow-up visit the proportion of such women in the counselled group who ceased smoking (9.3%) was significantly greater than in the control group (2.6%; P less than 0.05). The magnitude of this difference persisted through late pregnancy (11.8% vs. 4.3%; NS) and delivery (10.6% vs. 4.7%; NS). The differences between counselled women and controls in numbers of cigarettes reported smoked at first and last prenatal follow-up visits (2.4 and 2.1) and at delivery (2.0) were all statistically significant. While there was no effect of counselling on either serum thiocyanate or end expiratory carbon monoxide, the counselled group gained slightly more weight than controls during the study (0.47 vs. 0.44 kg per week among controls; NS), and their infants had modestly higher birthweight (44 g; NS).

Breath Tests↗
PubMed1992

Colorectal cancer screening: optimal compliance with postal faecal occult blood test.

Five approaches to postal faecal occult blood test (FOBT) were compared in a population sample of 966 subjects collected from three general practitioner patient lists in Southern Sydney. The highest compliance rate (59.8%) was achieved by a method using a general practitioner letter, with no dietary restrictions with FOBT. This was also the least expensive method. Compliance rates can be affected by incorrect address information and screenees not considering themselves to be current patients. An explanation from the family doctor addressed personally to the patient with an enclosed FOBT kit can achieve high compliance rates.

Aged↗
PubMed1992

Dose-dependent toxicokinetics of L-689,502, a potent human immunodeficiency virus protease inhibitor, in rats and dogs.

L-689,502, N-[2(R)-hydroxy-1(S)-indanyl]-5(S)-(1,1-dimethylethoxy- carbonylamino)-4(S)-hydroxy-6-phenyl-2(R)-(4-[2-(4- morpholinyl)ethoxy]phenyl)methyl hexanamide, is a potent inhibitor of human immunodeficiency virus-1 protease. The effect of dose on the elimination kinetics of L-689,502 was studied in rats and dogs. After i.v. administration, total plasma clearance of L-689,502 in rats decreased with increasing dose; the clearance decreased from 181 ml/min/kg at 1 mg/kg to 86 ml/min/kg at 20 mg/kg. Similar results were observed in dogs; clearance fell from 29 ml/min/kg at 0.5 mg/kg to 17 ml/min/kg at 10 mg/kg. Bile flow in rats was retarded in a dose-dependent manner after a single i.v. injection of L-689,502. The cholestatic effect was reversible and maximal at 5 mg/kg i.v. Consistent with the cholestatic effect, L-689,502 caused an increase in serum levels of aminotransferase. After i.v. administration of L-689,502 (10 mg/kg), alanine aminotransferase increased from 50 to 370 IU/liter and aspartate aminotransferase from 120 to 700 IU/liter. Moreover, pretreatment of rats with L-689,502 resulted in a significant decrease in the elimination kinetics of antipyrine and diflunisal, as well as of L-689,502 itself. Collectively, these results suggest that the dose-dependent kinetics of L-689,502 in rats and dogs are more likely due to hepatotoxicity caused by the drug than to capacity-limited metabolism.

Acetaminophen↗
PubMed1992

Selecting staff.

Explore the source record for details and available documents.

Interviews as Topic↗
PubMed1991

Global suppression of protein folding defects and inclusion body formation.

Amino acid substitutions at a site in the center of the bacteriophage protein P22 tailspike polypeptide chain suppress temperature-sensitive folding mutations at many sites throughout the chain. Characterization of the intracellular folding and chain assembly process reveals that the suppressors act in the folding pathway, inhibiting the aggregation of an early folding intermediate into the kinetically trapped inclusion body state. The suppressors alone increase the folding efficiency of the otherwise wild-type polypeptide chain without altering the stability or activity of the native state. These amino acid substitutions identify an unexpected aspect of the protein folding grammar--sequences within the chain that carry information inhibiting unproductive off-pathway conformations. Such mutations may serve to increase the recovery of protein products of cloned genes.

Amino Acid Sequence↗
PubMed1991

Thermal unfolding pathway for the thermostable P22 tailspike endorhamnosidase.

The conditions in which protein stability is biologically or industrially relevant frequently differ from those in which reversible denaturation is studied. The trimeric tailspike endorhamnosidase of phage P22 is a viral structural protein which exhibits high stability to heat, proteases, and detergents under a range of environmental conditions. Its intracellular folding pathway includes monomeric and trimeric folding intermediates and has been the subject of detailed genetic analysis. To understand the basis of tailspike thermostability, we have examined the kinetics of thermal and detergent unfolding. During thermal unfolding of the tailspike, a metastable unfolding intermediate accumulates which can be trapped in the cold or in the presence of SDS. This species is still trimeric, but has lost the ability to bind to virus capsids and, unlike the native trimer, is partially susceptible to protease digestion. Its N-terminal regions, containing about 110 residues, are unfolded whereas the central regions and the C-termini of the polypeptide chains are still in the folded state. Thus, the initiation step in thermal denaturation is the unfolding of the N-termini, but melting of the intermediate represents a second kinetic barrier in the denaturation process. This two-step unfolding is unusually slow at elevated temperature; for instance, in 2% SDS at 65 degrees C, the unfolding rate constant is 1.1 x 10(-3) s-1 for the transition from the native to the unfolding intermediate and 4.0 x 10(-5) s-1 for the transition from the intermediate to the unfolded chains. The sequential unfolding pathway explains the insensitivity of the apparent Tm to the presence of temperature-sensitive folding mutations [Sturtevant, J. M., Yu, M.-H., Haase-Pettingell, C., & King, J. (1989) J. Biol. Chem. 264, 10693-10698] which are located in the central region of the chain. The metastable unfolding intermediate has not been detected in the forward folding pathway occurring at lower temperatures. The early stage of the high-temperature thermal unfolding pathway is not the reverse of the late stage of the low-temperature folding pathway.

Binding Sites↗
PubMed1991

Identification of global suppressors for temperature-sensitive folding mutations of the P22 tailspike protein.

Suppressor mutations which alleviate the defects in folding mutants of the P22 gene 9 tailspike protein have recently been isolated (Fane, B. and King, J. (1991) Genetics 127, 263-277). The starting folding defects were in missense polypeptide chains generated by host amino acid insertions at different amber mutant sites. Fragments of genes carrying the amber mutations with and without their independently isolated suppressor mutations were cloned and sequenced. The parental nonsense mutations were located at Q45, K122, E156, W202, W207, Y232, and W365. Their conformational suppressors were single amino acid substitutions at a limited set of sites, V84 greater than A, V331 greater than A, and A334 greater than V. The V331 greater than A or A334 greater than V suppressors were independently recovered starting with different mutant sites suggesting that they acted by some global or general mechanism. When the V331 greater than A and A334 greater than V mutations were crossed into well-characterized temperature-sensitive folding (tsf) mutants at various sites in the tailspike protein, they suppressed all of the eight tsf mutants tested. Since the tsf defects destabilize folding intermediates rather than the native conformation, this result implies that the suppressors act in the folding pathway. Strains carrying the isolated suppressor mutations displayed no obvious phenotypic defect and formed native biologically active tailspikes. Thus, these single amino acid substitutions have striking influences on the efficiency of intracellular chain folding, without causing functional defects in the native protein.

Amino Acid Sequence↗
PubMed1991

Leukemia inhibitory factor receptor is structurally related to the IL-6 signal transducer, gp130.

Leukemia inhibitory factor (LIF) is a cytokine with a broad range of activities that in many cases parallel those of interleukin-6 (IL-6) although LIF and IL-6 appear to be structurally unrelated. A cDNA clone encoding the human LIF receptor was isolated by expression screening of a human placental cDNA library. The LIF receptor is related to the gp130 'signal-transducing' component of the IL-6 receptor and to the G-CSF receptor, with the transmembrane and cytoplasmic regions of the LIF receptor and gp130 being most closely related. This relationship suggests a common signal transduction pathway for the two receptors and may help to explain similar biological effects of the two ligands. Murine cDNAs encoding soluble LIF receptors were isolated by cross-hybridization and share 70% amino acid sequence identity to the human sequence.

Amino Acid Sequence↗
PubMed1991

Intragenic suppressors of folding defects in the P22 tailspike protein.

Within the amino acid sequences of polypeptide chains little is known of the distribution of sites and sequences critical for directing chain folding and assembly. Temperature-sensitive folding (tsf) mutations identifying such sites have been previously isolated and characterized in gene 9 of phage P22 encoding the tailspike endorhamnosidase. We report here the isolation of a set of second-site conformational suppressors which alleviate the defect in such folding mutants. The suppressors were selected for their ability to correct the defects of missense tailspike polypeptide chains, generated by growth of gene 9 amber mutants on Salmonella host strains inserting either tyrosine, serine, glutamine or leucine at the nonsense codons. Second-site suppressors were recovered for 13 of 22 starting sites. The suppressors of defects at six sites mapped within gene 9. (Suppressors for seven other sites were extragenic and distant from gene 9.) The missense polypeptide chains generated from all six suppressible sites displayed ts phenotypes. Temperature-sensitive alleles were isolated at these amber sites by pseudoreversion. The intragenic suppressors restored growth at the restrictive temperature of these presumptive tsf alleles. Characterization of protein maturation in cells infected with mutant phages carrying the intragenic suppressors indicates that the suppression is acting at the level of polypeptide chain folding and assembly.

Alleles↗
PubMed1991

The A/Mallard/6750/78 avian-human, but not the A/Ann Arbor/6/60 cold-adapted, influenza A/Kawasaki/86 (H1N1) reassortant virus vaccine retains partial virulence for infants and children.

Characteristics of avian-human (ah) and cold-adapted (ca) influenza A/Kawasaki/9/86 (H1N1) reassortant vaccine viruses were compared in 37 seronegative adults and 122 seronegative infants and children. The 50% human infectious dose (HID50) in infants and children was 10(2.9) and 10(2.6) TCID50 for the ah and ca vaccine, respectively. The ah influenza A/Kawasaki/9/86 reassortant was reactogenic: 24% of infants and children infected with greater than or equal to 100 HID50 had fever greater than or equal to 39.4 degrees C. Since H3N2 ah vaccines were previously shown to be adequately attenuated, it is reasonable to suggest that the genes that code for hemagglutinin and neuraminidase of the H1N1 virus apparently influence the reactogenicity of reassortant viruses derived from the avian influenza A/Mallard/New York/6750/78 donor virus. Because this avian virus does not reproducibly confer a satisfactory level of attenuation to each subtype of influenza A virus, it is not a suitable donor virus for attenuation of wild-type influenza viruses. In contrast, the ca A/Ann Arbor/6/60 donor virus reliably confers attenuation characteristics to a variety of H1N1 and H3N2 influenza A viruses.

Adult↗
PubMed1991

Simultaneous administration of two human-rhesus rotavirus reassortant strains of VP7 serotype 1 and 2 specificity to infants and young children.

Two rotavirus vaccine strains representing VP7 serotypes 1 and 2 derived by reassortment between a rhesus rotavirus master strain, MMU18006, and either of two human rotavirus strains were administered simultaneously to infants and young children to assess potential interactions between strains. Children were observed in a day care setting for 10 days after vaccine administration for clinical symptoms, evidence of vaccine transmission, and patterns of viral shedding. Serum and local antibody responses were measured. The ratio of input virus strongly influenced the amount of each strain recovered from the child. Regardless of dose of virus administered, the neutralizing antibody response to the VP7 glycoprotein, the serotype determinant, was diminished in a bivalent preparation compared with a monovalent vaccine. Additional strategies must be sought to induce immunity against the multiple serotypes of human rotavirus before broad immunity will be established.

Administration, Oral↗
PubMed1991

Evaluation of bovine, cold-adapted human, and wild-type human parainfluenza type 3 viruses in adult volunteers and in chimpanzees.

In an attempt to evaluate the level of attenuation of live parainfluenza type 3 virus (PIV3) vaccine candidates, we compared the responses of partially immune adult volunteers inoculated intranasally with 10(6) to 10(7) 50% tissue culture infective dose (TCID50) of bovine PIV3 (n = 18) or cold-adapted (ca) PIV3 (n = 37) with those of 28 adults administered 10(6) to 10(7) TCID50 of wild-type PIV3. The candidate vaccine viruses and the wild-type virus were avirulent and poorly infectious for these adults even though all of them had a low level of nasal antibodies to PIV3. To determine whether the ca PIV3 was attenuated, we then administered 10(4) TCID50 of ca PIV3 (cold-passage 12) or wild-type PIV3 intranasally and intratracheally to two fully susceptible chimpanzees, respectively, and challenged the four primates with wild-type virus 1 month later. Compared with wild-type virus, which caused upper respiratory tract illness, the ca PIV3 was highly attenuated and manifested a 500-fold reduction in virus replication in both the upper and lower respiratory tracts of the two immunized animals. Despite restriction of virus replication, infection with ca PIV3 conferred a high level of protective immunity against challenge with wild-type virus. The ca PIV3 which had been passaged 12 times at 20 degrees C did not retain its ts phenotype. These findings indicate that ca PIV3 may be a promising vaccine candidate for human beings if a passage level can be identified that is genetically stable, satisfactorily attenuated, and immunogenic.

Adaptation, Physiological↗