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Biomedical subjects

K Robbins

Publications and source records attributed to K Robbins.

At least 37 records · Page 2Linked to original sources
PubMed1990

Side effects of methylphenidate in children with attention deficit hyperactivity disorder: a systemic, placebo-controlled evaluation.

The frequency and severity of 17 side effects presumably associated with stimulant medication were assessed during a rigorous, triple-blind, placebo-controlled, crossover evaluation of methylphenidate, 0.3 and 0.5 mg/kg twice a day, in 83 children with attention deficit hyperactivity disorder. Side effects were rated by parents and teachers at the end of each weekly drug condition. Three children (3.6%) had side effects that were sufficiently serious to warrant immediate discontinuation of medication. Parent ratings indicated that only the side effects of decreased appetite, insomnia, stomachaches, and headaches increased significantly in frequency and severity during the two active medication doses as compared with the placebo condition. Fewer than half of the children experienced these side effects and among those who did, ratings of mean severity remained in the mild range. Teacher ratings showed little change over drug conditions, except on ratings of staring, sadness, and anxiety, which declined with increasing dose of medication. Parent ratings indicated that only the side effects of decreased appetite, insomnia, stomachaches, and headaches increased significantly in frequency and severity during the two active medication doses as compared with the placebo condition. Fewer than half of the children experienced these side effects and among those who did, ratings of mean severity remained in the mild range. Teacher ratings showed little change over drug conditions, except on ratings of staring, sadness, and anxiety, which declined with increasing dose of medication. Surprisingly, a high frequency of these behavior side effects were reported during the placebo condition. Stimulant medication within this therapeutic range, therefore, results in few, generally mild side effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

The response of aggressive and nonaggressive ADHD children to two doses of methylphenidate.

Differences between 37 aggressive and 37 nonaggressive children with attention deficit hyperactivity disorder (ADHD) were evaluated as was their response to two doses of methylphenidate (0.3 and 0.5 mg/kg) using a multimethod battery of behavior ratings, laboratory tests, and direct observations. Aggressive ADHD children differed little from nonaggressive ADHD children except that nonaggressives displayed more problems with inattentiveness at school than aggressives while mothers of aggressives reported more symptoms of psychopathology in themselves than mothers of nonaggressives. In their drug responding, aggressives and nonaggressives were quite similar. The few exceptions were on measures of conduct, on which the aggressives were initially rated as more extreme and subsequently showed the greater degree of improvement from medication than nonaggressives. Results replicated those of a previous study and further indicate that aggressive and nonaggressive ADHD children share a common disorder of ADHD but aggressives have more impaired family situations.

Adolescent↗
PubMed1988

The spread of AIDS.

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Gonococcal pilin variants in experimental gonorrhea.

When pilus+ Gc were introduced into a male subject's urethra, they gave rise to pilus+ variants whose pilin mRNAs differed from that of input Gc. The differences stemmed from the Gc genome's single complete pilin gene having undergone gene conversion by different partial pilin genes' sequences and by different length stretches of a single partial pilin gene. In some instances, the variant's pilin mRNA appeared to reflect two independent gene-conversion events that used sequences from two different partial pilin genes. The resulting variants' pilins exhibited antigenic differences compared with the pilin polypeptide of input Gc; these differences were discernible by immunoblotting with mAbs. Amino acid and antigenic changes occurred in a segment of the variants' pilin polypeptides that previously was thought to be conserved or constant in sequence.

Amino Acid Sequence↗
PubMed1987

Gene conversion variations generate structurally distinct pilin polypeptides in Neisseria gonorrhoeae.

Pilus+ to pilus- phenotype change occurs in Neisseria gonorrhoeae through gene conversion of the gonococcus' complete, expressed pilin gene by nucleotides homologous to the pilS1 copy 5 partial pilin gene; assembly missense pilin is synthesized but pili are not. Reversion to pilus+ occurs by a subsequent recombinational event that replaces the complete pilin gene's pilS1 copy 5-like sequence with nucleotides from a different partial gene to effect expression of an orthodox (i.e., pilus producing) pilin. Sibling pilus+ revertants of common parentage can carry different sequences in their expressed pilin genes because they have undergone nonidentical gene conversion events such as recombinations with sequences from different partial genes, or recombinations with different length nucleotide stretches of the same partial gene; either can yield structurally and antigenically variant pilin polypeptides.

Amino Acid Sequence↗
PubMed1987

Effects of recA mutations on pilus antigenic variation and phase transitions in Neisseria gonorrhoeae.

Intragenic recombination between the single complete pilin gene (expression locus) and multiple, distinct, partial pilin gene copies (silent, storage loci) is thought to account for the generation of pilus antigenic diversity and piliation phase (on-off) changes exhibited by Neisseria gonorrhoeae. The mechanisms operating in the genomic rearrangements associated with these forms of pilus variation were investigated through the study of isogenic strains of gonococci bearing either wild-type or altered recA alleles. Examination of the rates of pilus phase variation and the genetic basis for changes in piliation status displayed by these strains show that recA mediated homologous recombination is required for these high frequency events and confirm that the nonpiliated state results from mutations in the expressed pilin gene. In a strain that is deficient in recA mediated homologous recombination, pilus phase variation occurs at a 100-1000-fold reduced rate and results predominantly from one class of spontaneous frameshift mutations within the pilin structural gene.

Alleles↗
PubMed1986

Gene conversion involving the pilin structural gene correlates with pilus+ in equilibrium with pilus- changes in Neisseria gonorrhoeae.

Gonococci (Gc) exhibit pilus+----pilus- "phase transitions" at high frequency, but only some of the pilus- Gc can revert to pilus+ phenotype. We examined reversible phase transitions between pilus+ Gc and a particular pilus- variant (P-rp+ phenotype) whose pilin mRNA carries a unique block of nucleotides encoding an "assembly missense" pilin polypeptide. The results show that Gc pilus+ in equilibrium with P-rp+ transitions can result from intragenic recombination in which there is nonreciprocal exchange of partially homologous DNA sequences from a partial pilin gene (in silent, storage form) into the expression locus' complete pilin gene. Hence Gc pilus phase variation, like pilus antigenic variation, can occur by gene conversion of the pilin structural gene expression locus.

Bacterial Adhesion↗
PubMed1986

Piliation control mechanisms in Neisseria gonorrhoeae.

Gonococci (Gc) undergo pilus+ to pilus- "phase transitions" readily in vitro. In the present study we sequenced pilin mRNA from reverting, pilus- Gc by oligonucleotide primer extension and compared these pilin mRNA sequences with those expressed by their pilus+ predecessors and pilus+ revertants. The results suggest that genetic rearrangement within the pilin structural gene can generate defective pilin gene products, resulting in a pilus- phenotype. These pilus- Gc give rise to pilus+ revertants upon reconstitution of their modified pilin gene.

Bacterial Outer Membrane Proteins↗
PubMed1985

Pilus- gonococcal variants. Evidence for multiple forms of piliation control.

Pilus+ to pilus- transitions of gonococci (Gc) that involve rearrangement of pilin gene DNA yield the P-n phenotype, which is incapable of reversion (to pilus+). Reversion to pilus+ is found for nonpiliated Gc that have undergone no apparent pilin gene rearrangement. Among the reverting, nonpiliated Gc, two distinct phenotypes (P-rp- and P-rp+) occur and are differentiated according to their synthesis (or lack) of pilin subunits; both P-rp- and P-rp+ Gc contain pilin-specific mRNA. The occurrence of these different pilus- phenotypes strongly suggests that several mechanisms can account for changes in the piliation status of Gc; one of these involves pilin gene rearrangement but the others apparently operate at posttranscriptional levels. Reverting pilus- Gc may have a pathogenic advantage in being able to reversibly alter their host cell adherence-promoting surface properties through high frequency transitions in piliation status.

Bacterial Outer Membrane Proteins↗
PubMed1983

Simultaneous outbreaks of Guillain-Barré syndrome and Bell's palsy in Hawaii in 1981.

Simultaneous outbreaks of Guillain-Barré syndrome (GBS) and Bell's palsy occurred among residents of Hawaii during the three-month period June through August 1981. The outbreak of GBS (six cases) involved children, while the outbreak of Bell's palsy (22 cases) involved primarily adults. Four of the six patients with GBS had serological evidence of recent infection with cytomegalovirus (CMV) v none of 24 control subjects; no such association with CMV infection could be demonstrated for patients with Bell's palsy. The patients with GBS and Bell's palsy lived in widely scattered areas within the population centers of Hawaii, and no common exposures to specific places or events were identified. Testing for antibodies to respiratory pathogens suggested that a variety of antecedent viral infections, in addition to CMV infection, may have been associated with this unusual simultaneous cluster of illnesses.

Adult↗