PubMed Health⌕ Search

Biomedical subjects

R J Hoffman

Publications and source records attributed to R J Hoffman.

15 recordsLinked to original sources
PubMed1998

One face of a transmembrane helix is crucial in mechanosensitive channel gating.

MscL is a mechanosensitive channel in bacteria that responds directly to membrane tension by opening a large conductance pore. To determine functionally important residues within this molecule, we have randomly mutagenized mscL, expressed the genes in living bacteria, and screened for gain-of-function mutants with hampered growth. Expression of these genes caused leakage of cytoplasmic solutes on little or no hypo-osmotic stress. In excised patches, the mutant channels gated at membrane tensions that are less than that required for the gating of the wild-type MscL. Hence, the data suggest that the slowed or no-growth phenotype is caused by solute loss because of inappropriate gating of the channel. Most of the mutations mapped to the first transmembrane domain. When this domain is modeled as an alpha-helix, the most severe mutations are substitutions of smaller amino acids (three glycines and one valine) on one facet, suggesting an important role for this structure in MS channel gating.

Amino Acid Sequence↗
PubMed1995

The mtrB gene of Bacillus pumilus encodes a protein with sequence and functional homology to the trp RNA-binding attenuation protein (TRAP) of Bacillus subtilis.

The mtrB gene from Bacillus pumilus encodes a 76-amino-acid polypeptide with 77% identity to the trp RNA-binding attenuation protein (TRAP) from Bacillus subtilis. B. pumilus TRAP binds trp leader RNA from either B. subtilis or B. pumilus in a tryptophan-dependent manner. Altering threonine 52 to alanine eliminated RNA-binding activity of B. pumilus TRAP.

Bacillus↗
PubMed1994

Ultraviolet regulation of neuroendocrine and circadian physiology in rodents.

UV wavelengths can regulate neuroendocrine and circadian responses in some rodent species. Appropriately timed UV exposures can block the short photoperiod-induced collapse of the reproductive system, cause a rapid suppression of nocturnal melatonin synthesis, regulate melatonin rhythms and phase shift wheel running rhythms. These biological effects of UV are not dependent on the Harderian gland or melanin in the eye, but appear to be related to the degree of transmission through the ocular lens. Such results are consistent with the hypothesis that elements in the retina can transduce UV stimuli for circadian and neuroendocrine regulation.

Albinism↗
PubMed1993

Detection of Moloney murine sarcoma virus in tissues and cultured cells by the polymerase chain reaction.

The polymerase chain reaction was used for Moloney murine sarcoma virus (MoMuSV) detection in frozen and formalin-fixed, paraffin-embedded tissue sections and cultured cells isolated from MoMuSV-induced tumors. Rapid DNA extraction by proteinase K digestion, followed by CHROMA SPIN + TE-100 column purification proved to be satisfactory. Two pairs of overlapping primers, flanking 1026 base pair (bp) to 221 bp, allowed to choose among four different length of DNA-amplified segments. Although net amplification was obtained for frozen tissue and tumor cultured cells in all combinations of primers, the maximum specificity and sensitivity resulted with 602 bp fragment. This product was fully and adequately digestible using Apa I and Sau3A I restriction endonucleases. DNA extracted from paraffin-embedded sections yielded an amplification product only when the primer pair which delineated a 221-bp segment was used. This reproducible method could be useful for diagnostic and for pathogenetic investigations of MoMuSV infections.

Animals↗
PubMed1993

A temporal study of the lesions induced by MoMuSV-349.

We used time point studies to document the progression of neoplasms, haematologic abnormalities and associated lesions induced by Moloney murine sarcoma virus-349 (MoMuSV-349). BALB/c mice inoculated intraperitoneally with MoMuSV-349 first developed histologically discernible lesions at 14 days post-inoculation (d.p.i.). The initial neoplasms were characterized by whorls of fusiform or spindle-shaped cells enmeshing dense infiltrates of neutrophils and macrophages. By 21 d.p.i., clinical signs associated with MoMuSV-349 infection were evident. The distribution of the neoplasms was more widespread, although the histologic appearance of the tumours was very similar to that found at 14 d.p.i. All mice sacrificed at 28 d.p.i. exhibited characteristic clinical signs associated with MoMuSV-349, including moderate cachexia. Histologically, neoplasms observed at 28 d.p.i. contained a significant vascular component. By 35 d.p.i., all mice exhibited severe clinical signs (e.g. cachexia, dull hair coat, uneven gait). Histologically, all the neoplasms had a predominant vascular component. Non-neoplastic lesions, such as severe thymic atrophy and multifocal pulmonary haemorrhage, were commonly present. Mice sacrificed 42 d.p.i. were clinically, grossly and histologically similar to those sacrificed at 35 d.p.i. However, one difference found in the 42 d.p.i. group was the presence of rare rhabdomyosarcomas infiltrating the skeletal muscles. Mice inoculated with MoMuSV-349 developed severe neutrophilia and lymphopenia, and moderate anaemia. This study demonstrates that MoMuSV-349 induced angiosarcomatous neoplasms are characterized by stage development and severe haematologic and non-neoplastic abnormalities.

Animals↗
PubMed1993

A comparative endpoint study of lesions induced by MoMuSV-m1, MoMuSV-HT1, MoMuSV-124 and MoMuSV-349.

Different MoMuSVs produced predictable clinical, gross, and histologic similarities and differences when inoculated into susceptible hosts intraperitoneally. The neoplasms induced by MoMuSV-124 and MoMuSV-349 were histologically indistinguishable. The distribution of the neoplasms was the most widespread in these two groups. Histologically, the neoplasms induced by MoMuSV-124 and MoMuSV-349 were best described as angioproliferative. The neoplasms induced by MoMuSV-HT1 were most accurately described as fibrosarcomas. Histologically, the neoplasms induced by MoMuSV-m1 had characteristics common to neoplasms induced by MoMuSV-124 and MoMuSV-349, but with a less prominent vascular component. All mice inoculated with these MoMuSVs had moderate to severe thymic atrophy. The degree of thymic atrophy associated with both MoMuSV-124 and MoMuSV-349 was histologically more severe than that associated with MoMuSV-m1 and MoMuSV-HT1. Both MoMuSV-HT1 and MoMuSV-m1 had infiltrates of primitive myeloid cells within the spleen. In the case of MoMuSV-m1, there was an apparent leukaemia with infiltrates of similar cells within the bone marrow. With MoMuSV-HT1, these primitive cells were confined to the spleen. In summary, this study demonstrated that some of the different strains of MoMuSV (with the exception of MoMuSV-124 and MoMuSV-349), induced histologically distinct lesions in BALB/c mice.

Animals↗
PubMed1984

Clio, fallacies, and homosexuality.

Major fallacies occur in historical writing on male homosexuality. These include: the assertion of controversial assumptions as proven; attributing complex phenomena to a single cause; semantic distortion; ethnocentricism; and anachronism. History itself is fallaciously conceived as historical "forces" (historicism) and intrinsic "will" (the pathetic fallacy). Finally there is "tunnel history," viewing events outside of a broad historical context.

Europe↗
PubMed1980

Embolization of extensive peripheral angiodysplasias. The alternative to radical surgery.

We describe two patients with extensive pelvic and lower limb angiodysplasias, in whom hemodynamic complications subsequently developed. These have been treated by selective angiography and multiple percutaneous transcatheter embolizations with satisfactory results (1 1/2 to four years of follow-up). One patient had had three previous operations with no improvement; amputation was the only surgical alternative. In the other patient, hip disarticulation and hemipelvectomy was seriously considered because of cardiac failure not responding to medical therapy. We review the literature and use our cases to illustrate points of technique and reemphasize the essential role of therapeutic embolization in the management of extensive angiodysplasia.

Adolescent↗
PubMed1980

Some cultural aspects of Greek male homosexuality.

A brief examination of Greek social structures, history, and cosmology reveals several points about the nature of, and attitudes towards, male homosexual practices in the classical period. First, due to the overwhelming importance of the Hellenic family, few men seem to have engaged exclusively in homosexual acts. Second, historical sources for Attica indicate that, although most men may have married, homosexual behavior was widespread among all levels of society and was considered no more opprobrious than heterosexual behavior. Third, the Greek cosmology, with its unbounded sexuality and constant blurring of sex roles, provided an atmosphere in which homosexuality was regarded by Athenians as neither irreligious nor unnatural.

Cultural Characteristics↗
PubMed1978

NADP-specific glutamate dehydrogenase in Metridium senile (L.).

1. An NADP-specific glutamate dehydrogenase (E.C. 1.4.1.4) of mitochondrial origin has been detected in M. senile, a sea anemone. 2. Substrate specificity and starch gel electrophoresis experiments indicated an absence of the NAD(P) glutamate dehydrogenase (E.C. 1.4.1.3). 3. This NADP specific GDH activity appears to be the sole GDH activity in species of the animal phylum Coelenterata.

Animals↗
PubMedDate not supplied

Vices, gods, and virtues: cosmology as a mediating factor in attitudes toward male homosexuality.

Using historical and anthropological evidence, the article examines the relationship of the polytheistic and monotheistic cosmologies and attitudes toward sexuality, in particular, male homosexuality. The polytheistic cosmology included the ideas of the continuity of creation, the generative forces of the universe as a whole, and gender blurring in the realm of the supernatural. In the monotheistic cosmology the godhead (Yahweh) is unborn and does not father any generations, the universe is desexualized, and the conception of gender is rigidified. The author concludes that polytheism created the conditions for a wide variety of sexual expression and sex-role behavior and did not preclude any particular form of sexual activity. In contradistinction, the monotheistic cosmology was highly restrictive of permissible male and female behavior and sexual expression and conduct. Consequently, polytheism was able to embrace the crossing of gender lines and homosexual relationships while monotheism was incapable of making these accommodations.

Attitude↗