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Biomedical subjects

M L Anderson

Publications and source records attributed to M L Anderson.

At least 127 records · Page 7Linked to original sources
PubMed1980

Circadian rhythms and variability of the clinical electro-oculogram.

Clinical electro-oculograms (EOGs) were recorded from six normal subjects over 24 hr time periods for a total number of 70 EOG'S. Results indicate an inverse relationship exists between the light/dark (L/D) ratio and the dark-trough potential. No relationship was found between the light-peak potential and the L/D ratio. Both the dark-trough potential and the L/D ratio showed a circadian periodicity over working daylight hours and rather aberrant behavior in late evening and early morning hours. Circadian contributions to the L/D ratio are estimated to be between 20% and 50% of the total variability in the normal individuals studied. We suggest the optimal time for single measurements of EOG pathology should be around midday.

Adult↗
PubMed1979

Accumulation, nature, and possible functions of the malachite green affinity material in ejaculated human spermatozoa.

An electron microscopic study was conducted on human sperm over an incubation period of 5 to 6 hours in Tyrode's solution at room temperature. Examination of aliquots of the cells, fixed at timed intervals, with glutaraldehyde, malachite green, and postosmication revealed that malachite green affinity material (MGA-M) was barely discernible at first but did accumulate considerably upon standing. Biochemical analysis of MGA-M, which is extractable by glutaraldehyde, revealed that MGA-M is a mixture of extractable phospholipids and of their lyso-derivatives. Some of these substances have fusogenic properties; i.e., they are able to fuse together the membranes of two different cells. The appearance and accumulation of these fusogens occurred during the incubation period of 5 to 6 hours, which was previously shown to be required to capacitate human sperm in vitro. It is probable, therefore, that human sperm, during their initial period of incubation either in vivo or in vitro, not only become capacitated and undergo the acrosome reaction but also develop the fusogenic substance(s) which are necessary for the imminent fusion of their plasma membrane to the vitelline membrane of the mature oocyte.

Cytoplasm↗
PubMed1978

Incorporation of labelled degradation products of radioactive thymine into non DNA material.

When thymine auxotrophs are grown in the presence of methyl labelled [3H] or [14C] thymine which has been stored at 4 degrees C, two classes of material are labelled which are not DNA. One class sediments on neutral sucrose gradients with spontaneously single stranded Okazaki pieces, is unstable in alkali, migrates on alkaline gels as very small material and is digested by ribonucleases and micrococcal nuclease, but not by DNAase I. This class is presumably RNA. The second class sediments more slowly on both neutral and alkaline sucrose gradients than Okazaki pieces, but co-migrates on alkaline gels with DNA whose size is between 700 and 4000 nucleotides. It is not digested by alkali, ribonucleases or deoxyribonucleases. Its identity is unknown. The proportion of the total incorporated counts in these two classes depends on the time of storage of the thymine and is already sufficient to interfere with certain types of experiments when the thymine is only a few weeks old. Thymine is easily purified by paper chromatography and this purified thymine does not label the two non DNA classes of material. It is recommended that radioactive thymine be purified in this way before use.

Carbon Radioisotopes↗
PubMed1978

Environmental backgrounds of young Chinese nasopharyngeal carcinoma patients.

Twenty-four Chinese NPC patients under 25 years of age at the time of diagnosis were interviewed. The interviews were carried out in the presence of their families in 22 cases and concentrated on the environmental background of the subject's infancy and early childhood. An analysis of the results eliminated household inhalants, aerial contaminants, medicines, food therapy, spices, fresh foods and soya sauce as likely factors in carcinogenesis. The only remaining foods eaten by all subjects and worthy of consideration were laap cheung, salted fish and tau si. Salted fish was the most commonly eaten and the only one fed to babies. In childhood, the subjects had rarely or never been fed vegetables or fruits. Most had, since childhood, been characteristically sickly, inactive, withdrawn and choosy about their food. It would appear that consumption of salted fish and vitamin C-deficiency in early childhood are important environmental factors and that a certain personality type may be associated with an increased risk.

Adult↗
PubMed1973

Association of nascent polypeptide with 30S ribosomal subunits.

1. Crude extracts of Escherichia coli were used to synthesize nascent peptides under the direction of endogenous mRNA and in the presence of radioactive amino acids. Analysis of such extracts by sucrose-gradient centrifugation in low Mg(2+) concentration has shown that after 2min of incubation approximately 14% of the total labelled protein recovered on the gradient, in association with whole ribosomes, sediments with 30S ribosomal subunits; this value rises to approximately 24% after 30min of incubation. The labelled protein associated with 30S ribosomal subunits is insoluble in hot trichloroacetic acid. 2. Similar results were also obtained in extracts that synthesized polypeptides under the direction of either of the synthetic polyribonucleotides poly(A) or poly(A,G,C,U). In contrast, however, analysis of crude extracts programmed in protein synthesis by poly(U) has indicated that under these conditions 30S ribosomal subunits have no associated polyphenylalanine; similarly there is little associated peptide after programming of extracts by poly(U,C).

Amino Acids↗
PubMed1973

Association of nascent polypeptide and transfer ribonucleic acid with 30S ribosomal subunits.

1. Crude extracts of Escherichia coli programmed in protein synthesis by endogenous mRNA have incorporated amino acids into protein. Analysis of such extracts by sucrose-gradient centrifugation in low Mg(2+) concentration has revealed that 30S ribosomal subunits carry associated radioactive material of which a considerable proportion can be removed from ribosomes by treatment of pre-labelled extracts with puromycin. 2. Gradient analyses of incorporations carried out in the additional presence of added (32)P-labelled tRNA have indicated that tRNA sediments in the regions of the newly synthesized nascent protein and that both labels are associated with all ribosomal components detected on the gradients under the experimental conditions employed. 3. 30S ribosomal subunits carrying both (32)P and (14)C labels have been isolated, disrupted with sodium dodecyl sulphate, and analysed by chromatography on Sephadex G-200 columns. Both labels elute closely together and well away from a tRNA marker analysed under identical conditions. 4. It is proposed that 30S ribosomal subunits, isolated from extracts which have synthesized nascent peptides under the direction of endogenous mRNA, carry associated peptidyl-tRNA.

Amino Acids↗
PubMedDate not supplied

Variability of thymidylate synthase activity in whole blood cultures treated with FUdR.

Induction of some fragile sites including fragile X [fra(X)] depends on the depletion of thymidine monophosphate (TMP) from the culture medium. This can be accomplished by use of inhibitors such as 5-fluorodeoxyuridine (FUdR) and by culturing cells in medium deficient in folate and TMP. FUdR inhibits the activity of thymidylate synthase (TS), thereby depleting cells of TMP. To determine the degree of FUdR inhibition of TS under routine cytogenetic culture conditions, we modified the tritiated dUMP TS method for use in short-term whole blood cultures stimulated with phytohemagglutinin. TS inhibition was highly variable across whole blood cultures from 30 individuals exposed to FUdR during the last 24 hours of a 4 day culture. If an additional dose of FUdR was added 12 hours before harvest, TS inhibition usually increased. These findings have a potential impact on the use of FUdR for the diagnosis of the fra(X) syndrome.

Blood Cells↗
PubMedDate not supplied

Accuracy of assessment of the extent of examination by experienced colonoscopists.

One hundred colonoscopies were done. The colonoscopist noted whether the cecum had been intubated as well as the markers used to make this determination. With the colonoscope in position at maximum penetration, a radiologist independently determined its position using fluoroscopy, with a contrast agent delivered through the colonoscope. The cecum was entered in 86 of 100 cases. The tip of the colonoscope was at the level of the ileocecal valve in nine additional cases; the colonoscopist judged that the cecum was well seen in five of these nine. In one case, the colonoscopist overestimated the extent of the examination when transillumination in the right lower quadrant was the only confirming marker. When the more reliable markers (ileocecal valve, appendiceal orifice, converging indentations of the taenia coli in the cecal pole) were seen, no errors were made. Experienced colonoscopists are accurate in assessing the extent of colonoscopy and fluoroscopic confirmation is not routinely needed. When reliable markers are not seen during the examination, a barium enema, preferably with air contrast, should be done.

Cecum↗
PubMedDate not supplied

Onco-suppressor genes and their involvement in cancer (review).

Onco-suppressor genes are a heterogeneous set of genes that inhibit the cancer-related phenotype of cells. Because they are difficult to identify, only a few have been described. Evidence for their existence has mainly been indirect and comes from the following types of study. 1. Recessive cancer genes in higher and lower eukaryotes have been detected. If both alleles of these genes are deleted or inactivated, cancer develops. 2. Studies on cell hybrids have implicated genes which suppress various stages in the malignant conversion of normal cells e.g. immortalisation, morphological conversion and metastasis. 3. The isolation from virally induced transformants of flat, non-tumorigenic revertants in which expression of the transforming gene is not down-regulated suggests the presence of genes which suppress the effects of transformation. 4. Blocks to differentiation can be bypassed by inducing compounds or differentiation factors. 5. Studies on tumor inhibitory factors such as tumour necrosis factor and beta-TGF show that they have different effects on different types of cell-acting to promote growth in some cases and inhibit it in others. 6. The discovery of cis-acting negatice regulatory elements suggests that interaction of such elements with proteins may be important for control of gene expression particularly of infecting oncogenic viruses. 7. Suppression of the transformed phenotype of malignant cells by contact with normal cells that controls growth of neighboring cells. 8. The inhibition of proliferation of transformed cells by transfection with DNA from normal cells may be a useful method for cloning onco-suppressor genes. We discuss what is known and what is not known about this important class of gene.

Genes, Recessive↗