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Biomedical subjects

G Bennett

Publications and source records attributed to G Bennett.

At least 91 records · Page 5Linked to original sources
PubMed1991

Traffic through the Golgi apparatus as studied by radioautography.

The ability to radiolabel biological molecules, in conjunction with radioautographic or cell fractionation techniques, has brought about a revolution in our knowledge of dynamic cellular processes. This has been particularly true since the 1940's, when isotopes such as 35S and 14C became available, since these isotopes could be incorporated into a great variety of biologically important compounds. The first dynamic evidence for Golgi apparatus involvement in biosynthesis came from light microscope radioautographic studies by Jennings and Florey in the 1950's, in which label was localized to the supranuclear Golgi region of goblet cells soon after injection of 35S-sulfate. When the low energy isotope tritium became available, and when radioautography could be extended to the electron microscope level, a great improvement in spatial resolution was achieved. Studies using 3H-amino acids revealed that proteins were synthesized in the rough endoplasmic reticulum, migrated to the Golgi apparatus, and thence to secretion granules, lysosomes, or the plasma membrane. The work of Neutra and Leblond in the 1960's using 3H-glucose provided dramatic evidence that the Golgi apparatus was involved in glycosylation. Work with 3H-mannose (a core sugar in N-linked side chains), showed that this sugar was incorporated into glycoproteins in the rough endoplasmic reticulum, providing the first radioautographic evidence that glycosylation of proteins did not occur solely in the Golgi apparatus. Studies with the tritiated precursors of fucose, galactose, and sialic acid, on the other hand, showed that these terminal sugars are mainly added in the Golgi apparatus. With its limited spatial resolution, radioautography cannot discriminate between label in adjacent Golgi saccules. Nonetheless, in some cell types, radioautographic evidence (along with cytochemical and cell fractionation data) has indicated that the Golgi is subcompartmentalized in terms of glycosylation, with galactose and sialic acid being added to glycoproteins only within the trans-Golgi compartment. In the last ten years, radioautographic tracing of radioiodinated plasma membrane molecules has indicated a substantial recycling of such molecules to the Golgi apparatus.

Animals↗
PubMed1991

Psychological change during residence in a rehabilitation centre for female drug misusers. Part I. Drug misusers.

Fifty consecutive entrants to a year-long Christian residential rehabilitation programme for female drug misusers received a comprehensive psychological assessment on intake, 3 and 6 months later, and at completion of the programme. Significant changes were seen in emotional state, self-esteem, personality and attitudes to Christianity. Most of the changes occurred during the first 3 months, but changes in personality continued throughout the period of residence. The 11 women who completed the programme differed significantly from the others on their characteristics at intake; the 26 who dropped out during the first 3 months differed significantly from those who dropped out after that time. In both cases, the differences were at a clinically significant level. The importance of matching drug users to rehabilitation centres is discussed.

Adolescent↗
PubMed1991

Psychological change during residence in a rehabilitation centre for female drug misusers. Part II. Children of drug misusers.

This study examined psychological changes in children of female drug misusers who were living with their mothers in a residential rehabilitation centre. The results suggest that the childrens' behaviour and cognitive skills were not adversely affected, and that there were many benefits for drug addicted mothers retaining custody of their children whilst undergoing a rehabilitation programme. The implications of the possible detrimental effects of a mother failing to complete her rehabilitation programme on her children are discussed.

Achievement↗
PubMed1990

Molecular nature of in vivo mutations in human cells at the autosomal HLA-A locus.

The mutations present in vivo in normal human cells were studied at the HLA-A locus by isolating mutant lymphocytes using antibody-complement immunoselection and cloning at limiting dilution. The molecular basis for mutation in 127 mutant lymphocytes from 10 individuals was determined by studying a variety of polymorphic gene loci on both arms of chromosome 6. No change was detected in 78 mutants (61.4%), gene deletion was detected in 11 (8.7%), and mitotic recombination was detected in 38 (29.9%). Neither gene conversion nor chromosome loss was detected. These observations document the mechanisms responsible for gene loss in normal human cells in vivo, emphasize the importance of mitotic recombination, and indicate the similarity between mutational mechanisms in normal cells and in cancer cells.

Cells, Cultured↗
PubMed1989

Sexual practices and "beats": AIDS-related sexual practices in a sample of homosexual and bisexual men in the western area of Sydney.

One hundred and seventy-six men who had engaged in sexual activity with other men in the past six months were interviewed, in the western area of Sydney, about their sexual activities and knowledge as related to the acquired immunodeficiency syndrome (AIDS). Comparisons were made between men who had frequented "beats" (public toilets, parks or isolated roads where men meet for homosexual encounters) in the past six months, and those who did not use beats. One-quarter of those men who frequented beats reported beats as their only venue for meeting men for sexual contact, while other men reported them as one of many venues that they used to meet men. Although all interviewed men were engaging in sexual activities with men, 12 men described themselves as heterosexual, and 12% of those men who used beats, and 7% of the beat non-users, were married or in de-facto relationships. In comparing those who used beats with the beat non-users, 64% of beat users had engaged in sexual practices with between six and 50 different partners in the past six months compared with 8% of beat non-users. Beat users also were more likely to engage in unprotected anal intercourse with causal partners. Nineteen men claimed to be HIV-seropositive for the human immunodeficiency virus, with 11 of these men still engaging in high-risk sexual activities. The implications for AIDS education are discussed.

Acquired Immunodeficiency Syndrome↗
PubMed1989

A potential source for the transmission of the human immunodeficiency virus into the heterosexual population: bisexual men who frequent "beats".

Fifty-four actively bisexual men with recent sexual experiences with both men and women were interviewed as part of a wider study of 176 homosexual men, many of whom frequented "beats" (public toilets, parks and isolated roads where men meet for homosexual encounters). Forty-six per cent of the bisexual men were engaging in unsafe sexual practices with at least one man and one woman. Three of these men knew that they were seropositive for the human immunodeficiency virus, with two of these men engaging in unsafe sexual practices with some of their partners. Fewer than one-quarter of the bisexual men identified with or participated actively in aspects of organized, overt "gay" culture. So-called "closeted" bisexual men are suggested to be a major, but neglected, target for educational efforts against the acquired immunodeficiency syndrome.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Environment-dependent growth inhibition of human epidermal keratinocytes by recombinant human transforming growth factor-beta.

Transforming growth factor-beta (TGF-beta) purified from platelets is a potent growth inhibitor of several normal epithelial cell types in culture. In contrast, some carcinoma cell lines derived from tumors of these same tissues are resistant to this factor. Using recombinant human TGF-beta, the authors have confirmed these results with six normal human epidermal keratinocyte strains and four human epidermal squamous carcinoma cell lines. However, the sensitivity of normal cells to TGF-beta was found to depend on the culture conditions. When grown in a specialized nutrient medium supplemented with pituitary extract, keratinocytes were completely inhibited by the addition of 0.3 ng/ml TGF-beta. In contrast, when their growth was supported by cocultivation with 3T3 fibroblast feeder cells, 30- to 100-fold higher concentrations of TGF-beta were required to achieve comparable growth inhibition. This differential sensitivity occurred despite the fact that in both culture systems TGF-beta in the culture medium had a half-life of about 50 minutes, becoming tightly bound to the surface of the culture dish. Bound TGF-beta proved to be biologically active and stable for about a week in the absence of 3T3 feeder cells. Incubating 3T3 cells on TGF-beta-coated dishes, however, resulted in nearly quantitative removal and degradation of the TGF-beta within 2 days, permitting normal rates of keratinocyte growth. The binding of TGF-beta to surfaces and the ability of fibroblasts to attenuate its inhibitory activity for epithelial cells must be considered when evaluating in vitro models and in planning strategies for the use of this factor in vivo.

Animals↗
PubMed1989

Morphological and functional characteristics of myocytes isolated from human left ventricular aneurysms.

Isolated single myocytes were prepared from myocardium of developing ventricular aneurysms and from myocardium within the scar of chronic ventricular aneurysms. The morphology and function of the individual cells were compared. The cells from developing aneurysms were rod-shaped, with a distinct sarcomeric structure, but did not contract even in the presence of high calcium concentrations. The sarcomere length was significantly higher than that of cells from chronic aneurysms and approached the theoretical point at which no contraction can occur. Cells from chronic aneurysms were either rod-shaped and contractile, or rounded due to hypercontracture of the myofilaments. Electron microscopy of cells from developing aneurysms confirmed the presence of elongated sarcomeres, a loss of the actin-myosin interdigitation, and damage to the contractile proteins which was particularly evident in the thin filaments. Cells with similar characteristics have also been isolated from a ruptured, ischaemic papillary muscle. These changes, which are due either to ischaemia or to overstretching of cells, may account for the weakness of the wall of developing aneurysms and be a cause of rupture or enlargement.

Adult↗
PubMed1989

Ultrastructural localization of CMPase, TPPase, and NADPase activity in neurons, satellite cells, and Schwann cells in frog dorsal root ganglia.

Sections of bullfrog dorsal root ganglia were analyzed for cytidine monophosphatase (CMPase), thiamine pyrophosphatase (TPPase), and nicotinamide adenine dinucleotide phosphatase (NADPase) activity, and the distributions of these enzymatic activities were compared with those traditionally found in other cell types (e.g., CMPase: Golgi trans-sacculotubular network; TPPase: trans-Golgi saccule(s); NADPase: intermediate Golgi saccules). In the present study, CMPase activity in neurons was localized mainly to the Golgi trans-sacculotubular network and lysosomes, but sometimes also occurred at the ends of the trans and most distal intermediate Golgi saccules. A similar distribution was found in satellite and Schwann cells. TPPase activity in neurons occurred not only in the trans-Golgi saccule but also in the trans-sacculotubular network, lysosomes, and scattered tubular elements. In satellite and Schwann cells, activity was found in both the trans saccule and trans-sacculotubular network, and substantial activity often appeared in the more distal of the intermediate saccules. NADPase activity in neurons was usually absent from the intermediate Golgi saccules and was confined to the trans-sacculotubular network and lysosomes; however, activity was sometimes also found in the intermediate and/or trans-Golgi saccules. In satellite and Schwann cells, activity appeared consistently in both the trans-sacculotubular network and intermediate saccules, as well as in lysosomes. These distributions, especially in the case of TPPase and NADPase, differ substantially from the most frequently reported localizations of the above enzymes, indicating that the Golgi complex may exhibit considerable plasticity of structure and function in different cell types.

Animals↗
PubMed1989

An enzyme-linked immunosorbent assay to study human relaxin in human pregnancy and in pregnant rhesus monkeys.

A sensitive and specific double-antibody enzyme-linked immunoassay, using a synthetic analogue of human relaxin for standard and immunogen, was developed for the measurement of human relaxin (hRLX) in serum and plasma. No cross-reactivity was observed for human insulin, human insulin-like growth factor-I, hGH, human chorionic gonadotropin, hFSH, hLH or human prolactin. The assay was used to monitor RLX concentrations in samples from men, non-pregnant and pregnant women, and in pregnant rhesus monkeys infused with hRLX. RLX was not detected in serum from men nor from non-pregnant women, while a concentration of 600 ng/l was measured in pooled sera from two pregnant women (pregnancies achieved by in-vitro fertilization). Immunoreactive RLX (1.1 micrograms/g) was found in human corpora lutea taken from ectopic pregnancies at 7 weeks. In an experiment with a pregnant rhesus monkey infused with human RLX analogue, less than 1.5% of the maternal concentration was measured in the fetal circulation. Even though preliminary, these data suggest a low level of transfer of human analogue relaxin across the placenta in a rhesus monkey. Further studies of the physiology of RLX in human pregnancy will be facilitated by the availability of this immunoassay.

Amino Acid Sequence↗
PubMed1989

The assessment.

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Adult↗
PubMed1988

Synthesis of lens capsule and plasma membrane glycoproteins by lens epithelial cells and fibers in the rat.

The lens of the eye possesses a capsule which is a greatly hypertrophied basement membrane. To investigate the synthesis of glycoproteins destined for this capsule, 3H-fucose was injected into the vitreous body of intact rats weighing approximately 200 gm. The animals were killed from 10 min to 14.5 months later, and their lenses were processed for electron microscope radioautography. At 10 min after injection, more than 58% of the silver grains were localized to the Golgi apparatus of the lens epithelial cells. By day 1, the heaviest sites of reaction were the plasma membrane (more than 50% of total label), the basal cytoplasm, and the adjacent lens capsule, where a heavy band of reaction was seen. The remainder of the capsule exhibited a lighter diffuse reaction. In the lens fibers, the label was at first localized to clusters of vesicles but then migrated to the plasma membrane and to the region of the capsule adjacent to the basal surface of these fibers. Light microscope radioautographs of the lens capsule at later time intervals revealed that by 1 month after injection the diffuse reaction had disappeared, and only the strongly labeled band remained. By 14.5 months after injection, this band had migrated partially across the lens capsule, but the capsule itself had increased considerably in thickness. On the other hand, the distance between the labeled band and the free edge of the capsule had decreased from that seen at the time of injection.

Animals↗
PubMed1988

Mutations in human lymphocytes studied by an HLA selection system.

Human lymphocytes mutated at the HLA-A2 or HLA-A3 alleles were enumerated and studied by primary selection using antibody and complement, followed by limiting dilution cloning and secondary selection using immunofluorescence or antibody and complement. The geometric mean frequency of in vivo mutant lymphocytes was 3.08 X 10(-5) for the HLA-A2 allele and 4.68 X 10(-6) for the HLA-A3 allele. Mutagenesis by X-radiation or mitomycin produced a dose-related increase in mutant frequency. HLA-B phenotyping and Southern Analysis of the HLA-A gene suggested that mutation was frequently due to gene deletion, which was often substantial.

Alleles↗
PubMed1988

Radioautographic and cytochemical studies on the synthesis and intracellular transport of glycoproteins.

SUBCOMPARTMENTALIZATION OF GOLGI APPARATUS. There is much evidence that the Golgi apparatus may consist of various subcompartments which differ from one another in morphology, biochemical content and function. These subcompartments do not always have the same properties in different cell types, however, and may change properties in one cell type at different times. Important glycosyltransferases are distributed throughout the Golgi stack in some cell types, indicating that subcompartmentalization is not essential for the process of glycosylation in this organelle. PRESENCE OF GLYCOPROTEINS OUTSIDE OF THE SECRETORY-ENDOCYTIC PATHWAY. Preliminary biochemical, cytochemical and radioautographic evidence indicates that glycoproteins may exist outside of the secretory-endocytic pathway. The presence of radioautographic reaction over the nucleoplasm of Schwann and satellite cells as early as 5 minutes after 3H-fucose administration suggest either that fucosylated glycoproteins must migrate very rapidly to this location or that fucosylation occurs within the nucleoplasm itself.

Animals↗