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Biomedical subjects

K Greer

Publications and source records attributed to K Greer.

8 recordsLinked to original sources
PubMed1992

Regulation of chlorophyll apoprotein expression and accumulation. Requirements for carotenoids and chlorophyll.

Chlorophyll apoprotein accumulation and expression were examined in mutants of Chlamydomonas reinhardtii blocked at specific steps of carotenoid or chlorophyll synthesis. In the absence of carotenoids: 1) apoproteins of the core and light-harvesting complexes of photosystem I (CCI and LHCI, respectively) and photosystem II (CCII and LHCII, respectively) do not accumulate; 2) mRNAs for the CCI, CCII, and LHCII apoproteins accumulate to normal levels; and 3) synthesis of the chlorophyll apoproteins is differentially affected, or in some cases, not affected. In the absence of chlorophylls: 1) the apoproteins fail to accumulate; 2) mRNA levels for CCI and CCII apoproteins are relatively unchanged; 3) levels of LHCII apoprotein mRNA, but not rates of LHCII mRNA synthesis, are reduced in a light-dependent chlorophyll-synthesis mutant (ya12); and 4) synthesis of chlorophyll apoproteins is differentially affected or not affected in the case of several chloroplast-encoded apoproteins. These results demonstrate a direct role for carotenoids as well as chlorophylls in the stabilization of certain chlorophyll apoproteins and, for others, possibly in their translation. The data also indicate a role for chlorophyll synthesis in the stability of LHCII mRNA.

Animals↗
PubMed1992

Studies of matrix vesicle-induced mineralization in a gelatin gel.

Matrix vesicles isolated from fourth-passage cultures of chondrocytes were tested for their ability to induce hydroxyapatite formation in a gelatin gel in order to gain insight into the function of matrix vesicles in in situ mineralization. These matrix vesicles did not appear to be hydroxyapatite nucleators per se since the extent of mineral accumulation in the gel diffusion system was not altered by the presence of matrix vesicles alone, and in the vesicle containing gels, mineral crystals were formed whether associated with vesicles or not. In gels with these matrix vesicles and beta-glycerophosphate, despite the presence of alkaline phosphatase activity, there was no increase in mineral deposition. This suggested that in the gel system these culture-derived vesicles did not increase local phosphate concentrations. However, when known inhibitors of mineral crystal formation and growth (proteoglycan aggregates [4 mg/ml], or ATP [1 mM], or both proteoglycan and ATP) were included in the gel, more mineral was deposited in gels with the vesicles than in comparable gels without vesicles, indicating that enzymes within these vesicles were functioning to remove the inhibition. These data support the suggestion that one function of the extracellular matrix vesicles is to transport enzymes for matrix modification.

Adenosine Triphosphate↗
PubMed1990

Herpes labialis in parturients receiving epidural morphine following cesarean section.

A significant association exists between the use of epidural morphine (EM), reactivation of herpes labialis (HL) commonly known as coldsores, and pruritus in the obstetric population. A randomized prospective study was designed to eliminate previously identified confounding variables. Immediately following delivery, parturients having undergone cesarean section with epidural anesthesia with carbonated lidocaine (Xylocaine CO2, Astra, Mississauga, Ontario, Canada) with 1:200,000 epinephrine were sequentially randomized to receive either EM or im opioids for postoperative analgesia. One blood sample was collected for viral serology and two mouthwashes (day 0 and 2) were collected to determine oral viral shedding. The patients were observed daily for 5 days. Coldsores were cultured for herpes simplex virus (HSV). Of 187 patients, 96 received EM and 91 im opioids; herpes labialis occurred in 14 of 96 (14.6%) of the former but in 0 of 91 of the latter (P = 0.0004). All 14 experienced facial pruritus. The two groups were at equal risk for reactivation (seropositivity 64.6% and 62.6%, respectively). Analysis of data for those with positive HSV serology reveals 14 of 62 (22.5%) had EM and herpes labialis compared with 0 of 57 in the im group (P less than 0.0001). The incidence of oral viral shedding was low. Surgical stress, the local anesthetic solution, and epinephrine addition to the local anesthetic were eliminated as confounders. Stepwise logistic regression analysis revealed that EM and a history of herpes labialis in these patients were predictive for reactivating oral HSV.

Adult↗
PubMed1989

Promotion of embryonic chick limb cartilage differentiation by transforming growth factor-beta.

This study represents a first step in investigating the possible involvement of transforming growth factor-beta (TGF-beta) in the regulation of embryonic chick limb cartilage differentiation. TGF-beta 1 and 2 (1-10 ng/ml) elicit a striking increase in the accumulation of Alcian blue, pH 1-positive cartilage matrix, and a corresponding twofold to threefold increase in the accumulation of 35S-sulfate- or 3H-glucosamine-labeled sulfated glycosaminoglycans (GAG) by high density micromass cultures prepared from the cells of whole stage 23/24 limb buds or the homogeneous population of chondrogenic precursor cells comprising the distal subridge mesenchyme of stage 25 wing buds. Moreover, TGF-beta causes a striking (threefold to sixfold) increase in the steady-state cytoplasmic levels of mRNAs for cartilage-characteristic type II collagen and the core protein of cartilage-specific proteoglycan. Only a brief (2 hr) exposure to TGF-beta at the initiation of culture is sufficient to stimulate chondrogenesis, indicating that the growth factor is acting at an early step in the process. Furthermore, TGF-beta promotes the formation of cartilage matrix and cartilage-specific gene expression in low density subconfluent spot cultures of limb mesenchymal cells, which are situations in which little, or no chondrogenic differentiation normally occurs. These results provide strong incentive for considering and further investigating the role of TGF-beta in the control of limb cartilage differentiation.

Animals↗
PubMed1989

Vinyl versus latex gloves as barriers to transmission of viruses in the health care setting.

One type of vinyl and seven types of latex gloves without visual defects were tested with respect to their barrier function against high concentrations of three viruses of varying size: herpes simplex virus type 1 (HSV-1, 180 nm), human immunodeficiency virus type 1 (HIV-1, 100 nm), and echovirus type 9 (Echo 9, 25 nm). Viral suspensions of HSV-1 (10(8) TCD50/ml), HIV-1 (10(5) TCD50/ml), and echovirus type 9 (10(7.5)TCD 50/ml) were placed in an inverted glove finger immersed in media and maintained for 3 h at room temperature with sampling performed from outside the glove at 10 min, 30 min, 1 h, 2 h, and 3 h. No cytopathic effect (CPE) was identified after inoculation onto Vero cells or RhMK cells for HSV-1 and Echo 9, respectively, and reverse transcriptase activity was not detected in Hut 78 cells after inoculation of HIV-1 during any of the time intervals. Stretching of a glove finger for 18 h with repetition of the procedure with Echo 9 revealed no CPE. We conclude that under these experimental conditions, intact gloves act as effective barriers to the transmission of viral particles, including HIV in the health care setting.

Acquired Immunodeficiency Syndrome↗