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Biomedical subjects

P Hoffman

Publications and source records attributed to P Hoffman.

At least 109 records · Page 6Linked to original sources
PubMed1986

Anti-CALLA antibodies identify unique antigens on lymphoid cells and granulocytes.

The common acute lymphoblastic leukemia antigen (CALLA) is a 100-kd surface glycoprotein that is present on normal and malignant lymphoid cells. It is a useful marker for distinguishing between clinically important types of acute leukemia. Anti-CALLA monoclonal antibodies (MoAb) also react with mature myeloid cells (granulocytes), where they identify an antigen having a similar molecular weight (mol wt). We now report that the antigens detected by anti-CALLA MoAb on human lymphoid and myeloid cells differ in their behavior and chemistry. Surface-labeling studies indicate that the antigen on lymphoid cells has a mol wt of approximately 100 kd v 110 kd for that on granulocytes. When cells are metabolically labeled with 35S-methionine, differences in the mol wt of these antigens are again observed. Unlike the lymphoid antigen, expression of that on purified granulocytes is not modulated by incubation with specific antibody. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of proteolytic digests of the two antigens fails to clarify their chemical relationship. Thus the antigens detected on these two cell types may share an epitope(s) but be chemically distinct, or CALLA may exist in distinct forms and behave differently on lymphoid cells and granulocytes.

Amino Acid Sequence↗
PubMed1984

Respiratory mutants of Azotobacter vinelandii with elevated levels of cytochrome d.

A method is described for the isolation of respiratory mutants of Azotobacter vinelandii with increased amounts of d-type cytochrome by selecting for the inability to reduce tetrazolium red. Five stable mutants were obtained that had six-fold higher levels of cytochrome d, increased amounts of b-type and lower amounts of o-type and c-type cytochromes than the wild-type strain. Spectral alterations in cytochrome alpha 1 were also observed in the mutants. NADH and succinate oxidase activities of membrane particles were about two fold higher in the mutants compared to the wild-type strain. Ascorbate-N,N,N',N'-tetramethyl-p-phenylene diamine oxidase activity was barely detectable in membrane particles of the mutants. These results are consistent with an increase in the amount of the cytochrome d oxidase branch and a decrease in the amount and activity of the cytochrome o, alpha 1 oxidase branch in the mutants. Growth rates under oxygen-excess conditions and respiratory-linked proton translocation ratios of the mutant and wild-type stains were similar as were the photochemical spectral and kinetic properties of cytochrome d.

Azotobacter↗
PubMed1984

Limited choroidal hemorrhage associated with intracapsular cataract extraction.

In a prospective study, limited choroidal hemorrhage (LCH) was found in 16 of 521 eyes (3.07%) subjected to cataract extraction. It developed in ten of 69 highly myopic eyes (14.49%), three of 64 moderately myopic eyes (4.49%), and three of 388 eyes without clinically significant myopia (0.77%). A positive correlation was found between LCH and vitreous loss in myopic eyes. A cause and effect relationship was not established. Of systemic factors investigated, an association was found between LCH and cardiovascular disease (14 of 16 cases). The ophthalmoscopic appearance and clinical findings support the hypothesis that LCH and expulsive choroidal hemorrhage are manifestations of the same disease processes and share common pathophysiologic mechanisms. The cause in any one case is probably multifactorial.

Aged↗
PubMed1983

Search for a red cell enzyme or serum protein marker in amyotrophic lateral sclerosis and parkinsonism-dementia of Guam.

Frequency distributions were determined for 24 red cell enzyme and four serum protein systems, in an attempt to identify a genetic marker associated with either amyotrophic lateral sclerosis (ALS) or parkinsonism-dementia (PD), two progressive and fatal neurological disorders of unknown cause found with unusually high incidence among the Chamorros of Guam and the Northern Mariana Islands. No striking associations were identified between either disorder and any of the gene markers tested. Thus, no genetic cause is known for either disease; local environmental factors are most likely involved in pathogenesis.

Amyotrophic Lateral Sclerosis↗
PubMed1982

Nitrogen oxide reduction in Wolinella succinogenes and Campylobacter species.

Wolinella succinogenes cells and extracts reduced nitric oxide, and cells, but not extracts, reduced nitrous oxide. Formate-reduced W. succinogenes extracts generated the 573-nm peak in difference spectra seen previously in response to nitric oxide in denitrifiers. The type strains of several Campylobacter species did not reduce either gaseous oxide. Cells, but not extracts, of C. fetus subspecies (fetus and venerealis) reduced nitrous oxide; acetylene inhibited reduction. Neither cells nor extracts reduced nitric oxide.

Campylobacter↗
PubMed1981

Ultrastructure of hydrated proteoglycans using a pulsed plasma source.

During the past 10 years, attempts have been made to examine hydrated biological specimens by using wet chambers (at ambient temperature) [1-3] or cold stages (at -30 degrees C and below) during electron microscopic examination. Obtaining sufficient contrast of unstained hydrated biological samples has proven a considerable problem using both of these methods. Many fragile biological specimens, when examined hydrated, frozen or dried, are severely damaged by the electron beam and cannot be imaged by conventional scanning or transmission electron microscopy. In order to increase specimen contrast and eliminate electron beam induced trauma to the specimen, we have developed a wet-cell [4], which when used in concert with a pulsed plasma soft X-ray source, provides high contrast contact replicas of totally hydrated, unstained biological specimens. Although it has been postulated that hydrated unstained samples can be imaged by soft X-ray contact microscopy [5-7], to date there has been little success due to cell movement or degradation of the wet sample during the long exposure period necessary for an adequate imaging dose [8]. With the pulsed plasma source described in this study we have been able to use exposure times of approximately 40-60 ns while maintaining the sample in its hydrated state at atmospheric pressure. The resultant contact replicas exhibit good contrast and better than 30 nm spatial resolution when examined by conventional scanning electron microscopy.

Chemical Phenomena↗
PubMed1981

The attribution of personality traits: the stutterer and nonstutterer.

Three videotaped recordings were made of an adult male speaking in an interview situation. Tapes differed as a function of the fluency exhibited by the interviewed speaker (i.e., fluent speech, primary stuttering, secondary stuttering). Three audiotapes were recorded from the videotapes yielding six stimulus tapes. Independent groups of college students saw and/or heard one of the stimulus tapes, each described as an interview with a "male who stutters." The fluent audio- and videotapes were replayed to two additional groups but were described only as an interview with a "male." Groups rated the personality of the speaker after tape presentation. Results revealed no difference in personality trait assignment as a function of experimental variables. However, in a second experiment two groups of college students rated a hypothetical normal speaker and hypothetical stutterer as significantly different in personality attributes. Results are discussed with reference to stereotyping behavior.

Humans↗