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Biomedical subjects

M Snyder

Publications and source records attributed to M Snyder.

At least 199 records · Page 11Linked to original sources
PubMed1984

Glucose-6-phosphate-dehydrogenase-deficient erythrocytes have an impaired shape recovery mechanism.

In the human erythrocyte, the maintenance of the biconcave disc shape is important for cell viability as well as cell function. Previous studies have indicated the involvement of the hexose monophosphate shunt in the recovery of discoid shape after perturbation of echinocytic agents. In glucose-6-phosphate-dehydrogenase-deficient (Gd-) erythrocytes, the shunt activity is significantly decreased; thus, it might be expected that the shape recovery rate of Gd- erythrocytes would be decreased. We show here that shape recovery rates in the presence of the shunt stimulator methylene blue are as much as fivefold lower in Gd- erythrocytes. We also show that the protease inhibitor, N-alpha-tosyl-1-phenylalanine-chloromethyl ketone, has no effect on shape recovery in Gd-, whereas it increases normal cell shape recovery rates by 10-30-fold at 50 microM and causes cupping at 200 microM (see companion article by Alhanaty et al.). These changes are not due to reticulocytosis, as other hemolytic disorders do not show such changes. Further, both chronic hemolyzing Gd and A Gd variants show similar abnormal shape recovery behavior, whereas the extent of hemolysis is quite different between variants. Thus, the activity of the hexose monophosphate shunt appears to have a dramatic effect on the rate of reversal of echinocytosis. The lack of shunt activity of Gd cells would necessarily impair their ability to recover normal shape after perturbation.

2,4-Dinitrophenol↗
PubMed1983

Two gene families clustered in a small region of the Drosophila genome.

Three Drosophila genes that are clustered within 8 X 10(3) bases of DNA at the chromosomal region 44D have been identified and mapped, and the gene cluster entirely sequenced. The three genes are 55 to 60% homologous in DNA sequence. One gene contains an intron in its 5'-proximal protein coding sequence while the other two have none at this position; similarly, another gene has an intron in its 3'-proximal protein coding sequence which is not found in the other genes. All three genes are abundantly expressed together in Drosophila first, second, and early third instar larval stages and in adults, but they are not abundantly expressed in either embryonic, late third instar larval, or pupal stages. This gene family lies 11 X 10(3) bases away from another cluster containing four Drosophila larval cuticle protein genes plus a pseudogene. The cuticle genes are all abundantly expressed throughout third instar larval development. Thus, at least seven protein-coding genes and one pseudogene lie within 27 X 10(3) bases of DNA. Moreover, two small gene families can lie adjacent on a chromosome and exhibit different patterns of developmental regulation, even though individual genes within each clustered family are co-ordinately expressed.

Animals↗
PubMed1983

Relation of nursing activities to increases in intracranial pressure.

Increased intracranial pressure (ICP), a frequent finding in head trauma and other cerebral pathology, poses a serious threat to patients' prognosis and recovery. While considerable attention has been given to medical therapies used in reducing ICP, only recently has nursing looked at the effect care specific activities may have. In this descriptive and observational study of nine patients with cranial pathology and a Richmond bolt for measuring ICP, findings confirmed that nursing activities and environmental factors are associated with pressure increases. Respiratory care activities (mean 12.7 mmHg) and repositioning (mean 12.6 mmHg) resulted in the highest increases while lesser increases were associated with doing neuro-assessments (mean 7.2 mmHg) and spontaneous movements (mean 7.9 mmHg) of the patient. When the conversation was directed to the patient, the pressure increased in 33 of the 86 observations (mean 8.6 mmHg), in 21 of the 35 conversations about the patient, the mean pressure increase was 9.03 mmHg. Because many activities occurred simultaneously, it was difficult to derive the extent of elevation associated with a specific activity. Findings from this study and studies by other nurse researchers suggest actions nurses can use to minimize pressure increases. Many areas for further study exist.

Adult↗
PubMed1983

Selecting a model for use in curriculum evaluation.

In summary, our purposes have been to emphasize the importance of using a model in curriculum evaluation and to present guidelines for selecting an appropriate model. We have discussed our experience in selecting and using the Stake model only as an example. While a model does not eliminate all of the problems and frustrations of curriculum evaluation, it does make the task more manageable. It can also improve the quality of the evaluation and can even make curriculum evaluation enjoyable.

Curriculum↗
PubMed1982

Cuticle protein genes of Drosophila: structure, organization and evolution of four clustered genes.

Most of a 9 kb region of the Drosophila genome containing genes for several cuticle proteins has been sequenced. Five cuticle-gene-like sequences have been identified and mapped. Amino acid sequences of four of the five major third instar cuticle proteins have been determined. These four sequences are identical with those predicted from the sequences of four of the five genes. Two cuticle genes are transcribed in one direction and two in the opposite direction. The fifth cuticle-like gene is judged to be a pseudogene because several features of its structure and the absence of detectable transcripts suggest it is nonfunctional. Sequence comparisons indicate that it arose by an unequal crossing-over event involving two closely related and adjacent cuticle genes. Each of the four cuticle genes contains a signal peptide coding sequence interrupted by a short intervening sequence (about 60 bp) at a conserved site. Conserved sequences occur in the 5' mRNA untranslated region, in the adjacent 35 bp of upstream flanking sequence and at -200 bp from the mRNA start position in each of the cuticle genes. We discuss the structure, organization and evolution of these cuticle genes as a model small gene family.

Amino Acid Sequence↗
PubMed1982

Moods and memories: elation, depression, and the remembering of the events of one's life.

Three experiments investigated the influence of current mood states on the remembering of past events of one's own life. In the first and the second experiment, participants were induced to experience either the mood state of elation or the mood state of depression. They then reported events and experiences that had occurred during the previous week. In the first and the second experiments, using converging methods for assessing memory for past events, participants differentially reported past events and experiences whose affective quality was congruent with their current mood states: participants in elated mood states preferentially reported pleasant events and happy experiences, and participants in depressed mood states preferentially reported unpleasant events and unhappy experiences. Additional evidence from the second experiment suggests that the differential remembering of affectively positive or affectively negative events requires that, at the time of the remembering of these events, participants actually experience the mood states of elation or depression and not simply attempt to remember past events that could account for elation or depression. In the third experiment, designed to assess the plausibility of "experimental demand" interpretations of these findings, participants who experienced ostensibly effective mood inductions that were actually ineffective failed to manifest differential remembering of affectively positive and affectively negative events. Implications of this series of experiments for understanding the mechanisms that may link moods and memories, as well as the intrapersonal and the interpersonal consequences of mood states, are discussed.

Affect↗
PubMed1981

The cuticle genes of drosophila: a developmentally regulated gene cluster.

A 36 kilobase (kb) DNA segment of the Drosophila genome that contains several larval cuticle protein genes has been cloned and characterized. This segment maps at chromosomal locus 44D. It contains five genes, all of which are expressed at the same time of Drosophila development. Four of the genes are clustered within 7.9 kb of DNA and are abundantly expressed as poly(A)RNA in the epidermis of late third instar larvae but are not abundantly expressed in other developmental stages. A fifth gene lies 8 kb away from this cluster and is expressed at a much lower level in late third instar larval poly(A) RNA. Three of the four abundantly expressed genes have been shown to code for larval cuticle proteins; less decisive evidence indicates that the fourth gene also probably codes for a larval cuticle protein. Some of the genes are related in DNA sequence, and the proteins encoded in the cluster are related immunologically. Thus the cuticle genes encoded by the segment at 44D are members of a family of genes of common ancestry, which share the same pattern of developmental expression and reside in a small segment of the Drosophila genome.

Animals↗
PubMed1980

Construction of a composite tRNA gene by anticodon loop transplant.

By using sites for the restriction nuclease Hpa II, the information for the anticodon stem and loop of an altered Su+2 amber suppressor tRNA (a mutant of tRNAGln) has been transplanted to a specially prepared tRNATrp gene, which lacks it homologous anticodon stem and loop sequence. The resulting tRNA gene was cloned under lac operator-promoter control. The result is a functional, hybrid, amber-suppressor tRNA that can exhibit a moderately high efficiency in translation. It appears less efficient, however, than Su+7 tRNA, the amber suppressor that results from a direct anticodon mutation in tRNATrp. As judged by its suppressor spectrum, which is almost identical to the spectra of Su+2, and Su+7, the recomposed tRNA inserts glutamine at amber sites. This experiment is the prototype of a series of construction that examine the role of the nucleotides in the anticodon region.

Anticodon↗