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Biomedical subjects

M Robins

Publications and source records attributed to M Robins.

At least 19 recordsLinked to original sources
PubMed1997

Ultrasonic Monitoring of Oil-in-Water Emulsions Undergoing Depletion Flocculation

The paper describes a three-part experiment on flocculating emulsions in order to determine whether ultrasonic spectroscopy could be used to detect and characterize the flocculation process. Three emulsions which represented unflocculated, partially flocculated, and fully flocculated systems were prepared. They were characterized independently using direct microscopic examination and their creaming behavior. Ultrasonic spectroscopic measurements of the flocculating emulsions showed large changes during the flocculation process, which were not readily modeled using single particle scattering theory. The ultrasonic properties of the unflocculated emulsion did not change during the measurement period. The results demonstrate that ultrasonic techniques are capable of detecting the flocculation process. There is clear potential to use ultrasonic techniques to characterize flocculated structures, but more work is needed on the theoretical analysis of the interaction of ultrasound with particle aggregates. Copyright 1997Academic Press

Journal Article↗
PubMed1996

Chromatographic analysis of photodynamically significant porphyrin dimers and trimers.

Two porphyrin dimers, dihematoporphyrin dimer (DHD) and divinyl dimer (DVD), and two porphyrin trimers, dihematoporphyrin trimer (DHT) and divinyl trimer (DVT), have been analyzed utilizing isocratic ion-pair reversed-phase high-performance liquid chromatography. Results indicate that the vinyl porphyrins can be distinguished by three peaks appearing near 15, 38, and 42 min. The hematoporphyrin complexes are identified by the appearance of a peak located at 35 min. The DVT and DVD complexes present unique chromatographic markers at 28 and 15 min, respectively. Based on the location of these chromatographic markers, it was found that the Photofrin drug must contain the DVD and the DHT complexes, but does not contain the DVT complex. The purity of the DVT complex is compromised by the presence of DHD and DHT impurities.

Chromatography, High Pressure Liquid↗
PubMed1996

Weight modification efforts reported by black and white preadolescent girls: National Heart, Lung, and Blood Institute Growth and Health Study.

OBJECTIVE: This study tested four hypotheses: (1) a high percentage of 9- and 10-year-old girls are already trying to lose weight; (2) more white tha black girls are trying to lose weight; (3) more black than white girls are trying to gain weight; and (4) weight modification efforts of preadolescent girls are influenced by factors other than race, such as maternal criticism, body dissatisfaction, and socioeconomic status. DESIGN: Cross-sectional analysis of baseline data on 2379 girls 9 and 10 years of age, which consisted of 1213 black and 1166 white enrollees. RESULTS: Black girls were taller and heavier and showed earlier signs of puberty than white girls but were less dissatisfied with their weight, body shape, and body parts. Approximately 40% of 9- and 10-year-old girls reported that they were trying to lose weight. Of those girls classified in the fourth quartile of body mass index (BMI), approximately 75% were trying to lose weight. After adjusting for BMI, no significant black and white differences in the prevalence of those trying to lose weight were seen, but significantly more black than white girls were trying to gain weight. Multiple logistic regression identified a high BMI, the mother telling her she was too fat, and body dissatisfaction as the major factors associated with trying to lose weight. However, chronic dieting was only associated with a high BMI and the mother telling her she was too fat. An important predictor of girls who were trying to gain weight was being black, along with having a low BMI and the mother telling her she was too thin. CONCLUSIONS: Attempts at gaining weight are much more frequent among black preadolescent girls than their white counterparts. No racial difference was found between black and white girls in their efforts to lose weight or to practice chronic dieting. Because approximately 40% of 9- and 10-year-old girls are already trying to lose weight, pediatricians should capitalize on this concern by providing information on proper weight control techniques. Educational efforts should be directed to both the mother and the child, because weight control efforts of preadolescent girls are stimulated by their mothers' admonitions of being too fat or too thin. The high prevalence of dieting among the thinnest adolescent girls also needs to be addressed by pediatricians.

Black or African American↗
PubMed1995

Isolation and photodynamic effects of hematoporphyrin derivative components: a chromatographic analysis of the starting materials.

Twenty different fractions of hematoporphyrin derivatives (HpD) and eight fractions of an HpD dimer mixture were isolated utilizing isocratic reversed-phase ion-pair high-performance liquid chromatography. These fractions were characterized by UV-visible and fluorescence spectrophotometry. Fluorescence quantum yields and photokill efficiency for each fraction in PTK2 epithelial cells were obtained. Results indicate that some part of the photoactivity exhibited by HpD may be due to impurities present in the HpD starting material, hematoporphyrin-IX dihydrochloride, depending on its source. It was also found that hematoporphyrin D, a commercial acetylated product formed during synthesis of HpD, contained a higher percentage of monomers than would be expected.

Animals↗
PubMed1990

Experimental acute selenium intoxication in lambs.

The toxic effects of 5 mg per kg body weight of selenium given as sodium selenite orally or parenterally to growing lambs were examined. There was considerable individual variation in both susceptibility to intoxication and the degree of pathological change displayed. The results affirm the previously reported deleterious effects on the cardiovascular, respiratory and urinary systems and highlight damage to secondary lymphoid tissue in various organs. The use of a histochemical method for detecting selenium bonds demonstrated correlation between the density of reaction-product and histopathological changes within tissues, and showed the distribution of selenium in other tissues in which the gross and histopathological findings were non-specific or minimal.

Administration, Oral↗
PubMed1990

Effects of concurrent oral administration of monensin on the toxicity of increasing doses of selenium in lambs.

The effects of concurrent administration of monensin sodium on the toxicity of progressively increasing oral doses of selenium (0.2 to 2.4 mg per kg body weight), given as sodium selenite twice weekly, have been examined in growing lambs. To link the chemically determined selenium concentration in tissues with observable pathological changes, the histochemical method of Danscher, which visualizes selenium bonds within tissues, was utilized. Findings included damage to conduction and contractile myofibres in the heart, segmental sarcoplasmal necrosis with lysis and atrophic change in skeletal musculature and selective accumulation of Danscher reaction-product in damaged areas of the liver, kidney and secondary lymphoid tissue. Concurrent administration of monensin sodium at a constant safe dosage enhanced the toxicity of selenium as demonstrated by increased severity of the signs of intoxication, fatalities, tissue selenium concentrations and intensified gross, histopathological and histochemical changes.

Administration, Oral↗
PubMed1988

Measurement of coffee and caffeine intake: implications for epidemiologic research.

Reported associations between coffee or caffeine intake and benign breast disease, cancers, and cardiovascular diseases have generally been weak and inconsistent. The apparent discrepancies in these studies might be attributable to imprecision in the measurement of coffee and caffeine intake. A study of a random sample of 2,714 U.S. adults disclosed considerable misclassification of total caffeine intake and, to a lesser extent, coffee intake when the estimates were limited to only the number of cups of coffee consumed. Adjustment for the following factors is recommended: amount of caffeinated and decaffeinated coffee consumed both on weekdays and on weekends; the size of the container used; the method used to brew caffeinated coffee; and the amount of caffeine imbibed from tea and soft drinks. Intake of coffee varied markedly between seasons of the year and over time. Random misclassification of coffee and caffeine intake would have the effect of obscuring dose-response relationships to disease incidence.

Adult↗
PubMed1988

Confounders contributing to the reported associations of coffee or caffeine with disease.

The role of caffeine or coffee in causing or promoting the incidence of serious disease is equivocal. Two design factors may account for the discrepancies in reported findings on the effects of coffee drinking: (a) imprecision of measurement and (b) confounding variables. A study of 2,714 white U.S. adults disclosed that, of 32 risk factors analyzed by linear and logistic regression, only sex and cigarette smoking were found to be important potential confounders of caffeine and coffee intake. Partial R2 values of the other 30 risk factors were relatively small and were inconsistent for each sex. It is unlikely that any of these factors could explain any of the reported associations between caffeine or coffee consumption and certain diseases. However, certain weak associations with caffeine or coffee intake should be included in the study design when they are known to be risk factors of a disease under investigation. These factors for men are dietary fat intake, vitamin C intake, and body mass index; and for women are vitamin use, alcohol intake, stress, and perceived health status.

Adult↗
PubMed1987

A myopathy associated with muscle hypertonicity in the Cavalier King Charles Spaniel.

Clinical signs of electrically silent muscle hypertonicity are described in five Cavalier King Charles dogs. Biopsies of the biceps femoris and triceps muscles, when examined with the electron microscope, revealed evidence of sarcotubular and mitochondrial abnormalities. These included enlargement of the sarcoplasmic reticulum, hydropic degeneration of mitochondria, tubular proliferations in the vicinity of the triads and vacuolar invagination of mitochondria. The exact nature of these findings is not clear and it is suggested that utilization of tracer techniques would help to explain them.

Animals↗
PubMed1985

Epidemiology of brain tumors: the national survey of intracranial neoplasms.

A national survey, based on a probability sample of patients admitted to short-term hospitals in the United States during 1973 to 1974 with a discharge diagnosis of an intracranial neoplasm, was conducted in 157 hospitals. The annual incidence was estimated at 17,000 for primary intracranial neoplasms and 17,400 for secondary intracranial neoplasms--8.2 and 8.3 per 100,000 US population, respectively. Rates of primary intracranial neoplasms increased steadily with advancing age. The age-adjusted rates were higher among men than among women (8.5 versus 7.9 per 100,000). However, although men were more susceptible to gliomas and neuronomas, incidence rates for meningiomas and pituitary adenomas were higher among women.

Adenoma↗
PubMed1984

Histochemical studies on the zona reticularis of stress-susceptible pigs.

During an investigation into the role of the adrenal gland in stress susceptibility of pigs, the large lipid masses in the inner zona reticularis were seen to be particularly related to sex differences, although stress-susceptible castrates had significantly more lipid in this zone than had stress-resistant castrates. Significant histochemical differences were also found in the activity of glucose-6-phosphate dehydrogenase and succinic dehydrogenase between the sexes and between castrates of differing susceptibility to stress. The differences in histochemical activity suggest a different origin for some of the adrenocortical cells in the inner zona reticularis.

Adrenal Cortex↗
PubMed1975

Properties of oncornavirus RNA-directed DNA polymerase, the RNA template, and the intracellular products formed early during infection and cell transformation.

We have investigated three aspects of RNA turmor virus replication and cell transformation: (1) the properties of the purified avian and mammalian viral RNA-directed DNA polumerase, (2) some characteristics of the viral 60-70S RNA genome, 30-40S RNA subunits and intracellular viral RNA species, and (3) the interaction of the viral DNA polymerase with its RNA template early during infection and cell transformation by the murine sarcoma-leukemia virus (MSV[MLV]). Avian myeloblastosis virus (AMV) contains two forms of RNA-directed DNA polymerase, alpha, consisting of a single polypeptide of molecular weight 65,000, and alphabeta, consisting of two polypeptides of molecular weights 65,000 and 105,000. The alpha and alphabeta forms of AMV DNA polymerase both possess RNase H activity that requires free end termini on the ribopolymer and can degrade the RNA of the RNA-DNA hybrid in the 3' to 5' and 5' to 3' directions. But, alpha and alphabeta possess a different mode of exoribonuclease activity. While alphabeta RNase H is a processive exoribonuclease that degrades the polynucleotide chain to a core residue before attacking a second chain, alpha RNase H is a random exoribonuclease that releases the polynucleotide after each scission. Highly purified Moloney-MSV(MLV) DNA polymerase has both RNase H activity and the ability to read viral 60-70S RNA. These activities comigrate through five different steps of purification and are present at levels comparable to those found in purified AMV DNA polymerase. The MSV(MLV) 60-70S RNA genome and 35S RNA subunits were shown by periodate oxidationtritiated borohydride reduction to contain adenosine as the major 3'-terminal nucleoside. Poly (A) segments were isolated from viral 60-70S and 35S RNA by treatment with RNase A or RNase T1 and purified by afinity chromatography and gel electrophoresis. Viral poly(A) was shown to be present at the 3' terminus as -G(C,U)A190AOH. The similar sequence reported for poly(A) present in mammalian mRNA suggests that similar mechanisma are involved in the transcription and processing of both cellular and viral DNA sequences. Within transformed cells replicating MSV(MLV), viral 35S and 20S RNA were found in membrane-bound polyribosomes, whereas only 35S RNA was detected in free polyribosomes. The origin and function of 20S RNA is unknown. The early events during rapid infection and cell transformation of mouse 3T6 cells by the Harvey strain of MSV(MLV) were studied. By both autoradiographic analysis and molecular hybridization, viral DNA synthesis was detected in the cytoplasm by 1 hour after infection, reached a maximum at 2 hours, and subsequently decreased. Cytological chase experiments produced evidence that cytoplasmic viral DNA was transported to the nucleus. In situ hybridization experiments using radioactive viral DNA product as a probe demonstrated the rapid association of viral DNA sequences with the chromocenters of interphase nuclei and with the centromeric heterochromatin regions of some chromosomes.

Avian Myeloblastosis Virus↗