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M D Cooper

Publications and source records attributed to M D Cooper.

476 records · Page 27Linked to original sources
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A novel cell surface molecule on early B-lineage cells.

B cells and their antibody-secreting progeny represent one of several differentiation pathways that haematopoietic stem cells (HSC) may enter. Cells representing intermediate stages between HSC and B cells have been identified in mammalian haematopoietic tissues and studied intensively over the past decade. This population of early B-lineage cells, termed pre-B, is characterized by cellular proliferation and an orderly cascade of immunoglobulin gene rearrangements, a combination of events leading to the generation of clonally diverse B cells which then migrate to peripheral lymphoid tissues. It remains to be determined what elements determine the polyclonal growth of pre-B cells, how immunoglobulin gene rearrangements are regulated, and what happens to pre-B cells undergoing 'non-productive' immunoglobulin gene rearrangements. These issues could be resolved more easily if early B-lineage cells could be identified precisely and isolated. Here, we describe a cell surface glycoprotein that is selectively expressed by pre-B and newly formed B cells in murine haematopoietic tissues. The molecule, a homodimer formed by disulphide-linked chains of relative molecular mass (Mr) 140,000, is identified by a mouse monoclonal alloantibody called BP-1.

Animals↗
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Comparison of various icing times in decreasing bone metabolism and blood flow in the knee.

In a previous study we used technetium-99m bone scans to show that cooling a knee for 20 minutes with a standard ice wrap will decrease soft tissue blood flow by a mean of 26%, and skeletal blood flow and metabolism by 19%. The present study examined the effects of shorter and longer icing periods to determine minimum cooling time for a measurable and consistent decrease, and time to produce maximal decrease within a safe period of icing (< 30 minutes). Thirty-eight subjects were studied. An ice wrap was applied to one knee for an assigned time (5, 10, 15, 20, or 25 minutes). Triple-phase bone scans of knees were obtained; mean percentages of decrease in the iced knee for each of the five time groups at each of the three phases of the bone scan were calculated and compared. Mean decreases of 11.1% in soft tissue blood flow, and 5.1% in skeletal metabolism and blood flow were measured at 5 minutes; maximums of 29.5% and 20.9%, respectively, were obtained at 25 minutes. A small but consistent decrease in soft tissue blood flow and skeletal blood flow and metabolism in a knee appear to be obtained with as little as 5 minutes of ice application. This effect is time-dependent and can be enhanced three- to four-fold by increasing the ice application time to 25 minutes.

Adult↗
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B-cell ontogeny in the chicken.

We conclude that our data are most consistent with the hypothesis that individual bursal stem cells give rise to multiple clones of B lymphocytes by a preprogrammed sequence of variable (V) region genes. The alternate hypothesis that each stem cell gives rise to one B cell expressing but one set of VH genes could only fit our data if the additional assumption is made that each stem cell is preprogrammed to give rise to an unique B-cell clonotype at a fixed time during development. Since we were unable to influence the pattern of expression of clonotypic diversity by modifying the exposure to antigens and since random somatic mutations would seem an inefficient mechanism for systematic generation of the diversity, we favor the possibility of a genetic mechanism involving an orderly pairing of germ-line VH and VL genes. The corollary of this hypothesis is that V-region diversity is generated first and Ig-class diversity is secondarily expressed within each clone by a switch mechanism for the sequential expression of CH genes.

Animals↗
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A survey of expanded duties usage in Indiana: a pilot study.

PURPOSE: The information presented in this pilot study was obtained as part of a 1990 survey of Indiana dentists. This portion of the study determined the number and types of expanded duties delegated to dental hygienists and the relationship of this information to their employer's year of graduation. METHODS: A 10% random sample of Indiana dentists was sent a questionnaire that asked each practitioner's specialty and year of graduation from dental school. In addition, the number of dental hygienists and assistants employed in the practice and the frequency of selected expanded function procedures they performed were determined. Statistical treatment of the survey data was accomplished by frequency tabulations on procedures delegated; principal component analysis applied to a select number of measures; and Student's t-test to variables related to office environment (total years experience, total staff, percentage employing dental hygienists, percentage employing full-time dental hygienists, number of procedures employed, and graduation year of dentist). The level of significance selected for the t-test analysis was .05. RESULTS AND CONCLUSIONS: Seventy-four questionnaires were returned out of 231 mailed (32% response rate). Of the expanded functions listed on the survey, the procedures most widely delegated to dental hygienists were amalgam polishing and sealant placement. The placement of resin and amalgam restorations was rarely performed by dental hygienists. Based on a principal component analysis, two office environments were defined. Type A offices had dentists with a mean graduation date of 1965.9. Type B offices had dentists with a mean graduation date of 1977.8, significantly larger staff sizes, and employed a higher percentage of full-time dental hygienists. Moreover, dental hygienists employed in Type B offices also performed a greater number of expanded function procedures than did dental hygienists in Type A offices.

Dental Assistants↗
PubMedDate not supplied

Characterization of cysteamine as a potential contraceptive anti-HIV agent.

Cysteamine (beta-mercaptoethylamine, or MEA) is a thiol-reducing agent and has anti-HIV activity. Because of these properties, cysteamine was evaluated as a vaginal contraceptive and tested for its effects on sperm function and on other sexually transmitted microbes. Cysteamine was contraceptive in the rabbit. Conception was inhibited completely when sperm were pretreated with 500 microg/ml cysteamine and was inhibited by more than 60% when 7.5 mg cysteamine was applied vaginally as a suspension in 50% K-Y Jelly. Cysteamine had multiple effects on spermatozoa. Both acrosin (EC 3.4.21.10) and hyaluronidase (EC 3.2.1.35) were reversibly inhibited by cysteamine. Calculated IC50 values were 370 microg/ml and 150 microg/ml for acrosin and hyaluronidase, respectively. Cysteamine behaved as a poor spermicide when activity was measured by the 30-second Sander-Cramer test. However, sperm motility was inhibited completely when cysteamine was preincubated for 10 minutes prior to motility evaluation, at concentrations as low as 50 microg/ml. The calcium ionophore A23187-induced human acrosome reaction was inhibited by cysteamine (IC50 = 0.5 microg/ml). Neither herpes simplex virus nor Neisseria gonorrhoeae was affected by cysteamine at concentrations as high as 500 microg/ml and 100 microg/ml, respectively. Cysteamine appears to have no effect on normal vaginal flora (i.e., lactobacillus). These results, together with published data, strongly support the further development of cysteamine as a topical contraceptive anti-HIV agent.

Acrosin↗