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J Bryan

Publications and source records attributed to J Bryan.

216 records · Page 12Linked to original sources
PubMed1971

Are cytoplasmic microtubules heteropolymers?

Colchicine-binding protein, considered to be microtubule protein, was purified from chick embryo brain by column chromatography in one step on DEAE-Sephadex. The active colchicine-binding unit is a dimer, MW 115,000 +/- 5000, which is composed of two nonidentical monomeric units. The two subunits are separable by urea-acrylamide gel electrophoresis after they have been reduced and acetylated. Sodium dodecyl sulfate-acrylamide gel electrophoresis indicates that the subunits both have molecular weights of 55,000 +/- 2000. The amino-acid compositions of the two subunits showed statistically significant differences in six amino-acid residues. These results indicate that colchicine-sensitive cytoplasmic microtubules are heteropolymers.

Amino Acids↗
PubMed1970

Precipitation of proteins by vinblastine and calcium ions.

We have found that vinblastine sulfate can precipitate a number of proteins in addition to microtubule protein. Those proteins which precipitate with vinblastine sulfate, all of which were derived from structure, also precipitate with Ca(2+) ions. Our results suggest that vinblastine sulfate, presumably acting as a cation, precipitates proteins by combining with sites which can also combine with Ca(2+) ions.

Animals↗
PubMed1970

The isolation of a major structural element of the sea urchin fertilization membrane.

Procedures for isolating the contents of the cortical granules from the ova of the sea urchin, Strongylocentrotus purpuratus, are reported. Dithiothreitol is used to remove the vitelline coat; the "demembranated" eggs are then subsequently activated with butyric acid. By means of these procedures, the hyaline protein and crystalline or paracrystalline material have been isolated from the cortical granules. The crystalline material consists of sheets of cylinders or tubules 150-200 A in diameter. This material is believed to be a major structural element of the fertilization membrane which, in the absence of the vitelline coat, does not form.

Animals↗
PubMed1970

On the reconstitution of the crystalline components of the sea urchin fertilization membrane.

The characteristics of the reconstitution of a crystalline component of the sea urchin fertilization membrane are presented. The reassembly of large aggregates of cylindrical or tubular components is effected by the addition of calcium or other divalent cations. The reassembly requires a slightly alkaline pH and is little affected by increasing ionic strength. Reassembly is strongly inhibited by treatment with reducing agents such as dithiothreitol. The role of this protein in the formation of the fertilization membrane and its possible relation to the calcium-insoluble proteins of the mitotic apparatus are discussed.

Animals↗
PubMedDate not supplied

Toward understanding age-related memory loss in late adulthood.

BACKGROUND: While laboratory tests indicate that older adults typically perform more poorly than do younger adults on many types of memory tasks, the question arises as to whether, or to what extent, it is valid to attribute these differences to ageing per se or to some variable or class of variables that intervene between age and remembering. OBJECTIVE: The purpose of this review is to present three current views that might explain the relationship between age and remembering. They can be construed as variants on resource theories and include: the processing speed hypothesis, the executive function hypothesis, and the common cause hypothesis. METHODS: The review samples results pertinent to these hypotheses that derive from behavioural research. Studies involving various imaging techniques were considered beyond the scope of the review. RESULTS: The balance of research strongly implicates reductions in the speed of information processing as a fundamental contributor to normal age-related memory loss. Nonetheless there are circumstances where other mechanisms, such as working memory, executive function, and sensory processes, are important. CONCLUSION: Despite the phenomenological and empirical reality of age-related memory loss and the breadth of attempts to explain it, much work remains to be done to understand why it occurs. Contemporary debates about the nature and means of identifying shared and unique effects promise to shape future directions for research on memory aging.

Adult↗
PubMedDate not supplied

Challenges to understanding age-related memory loss in late adulthood: an introduction.

BACKGROUND: In the first 1999 issue of Gerontology several current hypotheses of age-related memory loss were canvassed. OBJECTIVE: In hopes of fostering debate and further consideration of factors implicated in memory loss in late adulthood, commentaries were sought from a number of prominent cognitive ageing researchers on this review. METHODS: Four commentaries were received and are briefly distilled in this preamble to them. RESULTS: The papers elaborate on several themes raised in the original review, articulate assumptions implicit in the review, question the techniques used to assess mediational hypotheses, and suggest factors omitted from the review that need also to be considered. CONCLUSION: Despite an extensive literature on memory ageing, we are still a long way from understanding the mechanisms responsible for it. While considerable progress has already been made, over-reliance on between-person analyses, ambiguity in underlying constructs, and omission from consideration of key situation-specific characteristics of a memory episode may all contribute to a less than definitive understanding of memory ageing.

Aged↗
PubMedDate not supplied

Diabetes, parental diabetes, and obesity in Oklahoma Indians.

The relationship between diabetes and parental diabetes status and obesity in Oklahoma Indians was studied. Data from 2095 adult Oklahoma Indians (1085 type II diabetic subjects and 1010 nondiabetic subjects) through a complete physical examination and personal interview showed a strong association between diabetes and parental diabetes status. Frequency of diabetes among siblings was significantly higher in families with affected parents than those without diabetic parents. No significant difference was found between families with one diabetic parent and those with two diabetic parents. The diabetic individuals were more obese than the nondiabetic individuals at age 18 and at interview. Obesity was defined as percent body mass index greater than 120. After adjusting for possible age and sex effects, the risk of diabetes for the obese was estimated as almost twice that for the nonobese.

Adult↗
PubMedDate not supplied

The origin of 1-(3-pyridyl-N-oxide)ethanol as a metabolite of 3-acetylpyridine.

1. 3-Acetylpyridine was metabolized extensively to 1-(3-pyridyl)ethanol when the hepatic enzyme source was the soluble fraction (140,000 g supernatant). 3-Acetylpyridine-N-oxide was identified as a metabolite using the 10,000 g or the microsomal fraction. 2. 1-(3-Pyridyl-N-oxide)ethanol was not detected as a metabolite of 1-(3-pyridyl)ethanol using tissue preparations. However, 3-acetylpyridine was formed in trace amounts when the alcohol was incubated with the 10,000 g or the microsomal fraction. 3. Incubation of 3-acetylpyridine-N-oxide with the soluble or 10,000 g fraction resulted in the formation of 1-(3-pyridyl-N-oxide)ethanol (keto-reduction) as the major metabolite. 3-Acetylpyridine was formed in trace amounts (N-oxide reduction) with the 10,000 g and the microsomal fractions.

Animals↗
PubMedDate not supplied

Salinity tolerance of Anopheles farauti Laveran sensu stricto.

To assess the salt tolerance of the malaria vector Anopheles farauti sensu stricto, larvae were collected from a freshwater environment on the outskirts of Honiara, Solomon Islands and placed in trays containing water with salinity varying from freshwater to seawater. Dead larvae and pupae and emerged adults were recorded and preserved. Most adults and nearly half of the larvae and pupae were then subjected to DNA analysis for species identification. No adult An. farauti emerged after prolonged immersion of larvae in undiluted seawater (3.5% salinity), although temporary immersion before pupation was compatible with survival. Salinities of up to 2.2% to 2.5% were compatible with good survival and adult emergence, at least from fourth instars. The results suggest that higher salinities may slow larval development and show that mortality at a given salinity is not uniform.

Animals↗
PubMedDate not supplied

Efficacy of mass single-dose diethylcarbamazine and DEC-fortified salt against bancroftian filariasis in Papua New Guinea six months after treatment.

The efficacy of two diethylcarbamazine (DEC) treatment strategies to control bancroftian filariasis, diethylcarbamazine-fortified salt (DEC-FS) and a single DEC dose on mass administration, was evaluated in two communities in Papua New Guinea with pretreatment antigen prevalence of 55% and 71%. In the first community 0.2% w/w diethylcarbamazine-fortified salt was distributed monthly to accepting households at no cost for 12 months. In the second community a single DEC dose based on body size but designed to give about 6 mg/kg was administered to eligible acceptors. Despite wide variation in antigen prevalence among study villages there were marked reductions in prevalences under both treatment strategies. Among individuals antigenaemic on day 0, DEC-FS and a single DEC dose gave filaria antigen clearance rates of 43% and 13%, respectively. In the salt-treated community the incidence of antigenaemia after 6 months in acceptors from households that received 5 kg or more of DEC-FS was 14% whereas in those receiving less than 5 kg salt was 4%. The incidence rates in the second community in those that received < 2.5 and > or = 2.5 tablets were 16% and 8%, respectively. The two treatment strategies were simple to manage and appropriate for developing countries and were widely accepted. DEC-FS was more efficacious than single-dose DEC tablets but a single administration of DEC tablets is easier to administer.

Adolescent↗