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Biomedical subjects

R C Smith

Publications and source records attributed to R C Smith.

At least 199 records · Page 11Linked to original sources
PubMed1990

The face lift and ancillary procedures.

In this article, face lift, forehead lift, and blepharoplasty procedures are addressed. Special emphasis is made on anatomical and surgical guidelines. Some results and complications of the different procedures are presented.

Eyelids↗
PubMed1990

Nonspecific effects of oligodeoxynucleotide injection in Xenopus oocytes: a reevaluation of previous D7 mRNA ablation experiments.

Microinjection of oligodeoxynucleotides (ODNs) complementary to cellular mRNAs has been advanced as an experimental approach to degrade target mRNAs in vivo and thereby obtain information as to the function of their cognate proteins. It is shown here that ODNs can induce a variety of aberrations in cell metabolism and structure when injected into Xenopus oocytes. Examination of histological sections of ODN-injected oocytes revealed the frequent abnormal accumulation of heavily staining basophilic material in the area of the germinal vesicle (gv). Ultrastructural analysis detected further abnormalities including blebbing of the plasma membrane, anomalous cytoskeletal structures, hyperorganised annulate lamellae, hyperinvagination of the gv, and formation of irregular nucleoli within the gv. Analysis of newly synthesised proteins by [35S]methionine radiolabelling of oocytes demonstrated that ODN injection can trigger a general decrease in both label uptake and protein synthesis. Qualitative effects on protein synthesis could also be observed, particularly a decrease in synthesis of high molecular weight proteins. The severity of ODN-induced effects is dose-dependent and highly variable from ODN to ODN. The previously reported delay in progesterone-induced maturation observed in oocytes depleted of the maternal mRNA D7 by ODN-directed degradation (Smith R. C., Dworkin M. B. and Dworkin-Rastl E. (1988) Genes and Devpt. 2, 1296-1306) is most likely a result of nonspecific ODN effects in the oocyte. Oocytes injected with effective antisense D7 ODNs that do not display detectable side effects matured with normal kinetics.

Animals↗
PubMed1990

Oligosaccharins from xyloglucan and cellulose: modulators of the action of auxin and H+ on plant growth.

UNLABELLED: The dose/response curve for auxin's action as a plant growth promoter is extremely wide. How does the cell vary its response to such a wide range of signal intensity? We suggest that cell wall-bound cellulase, and the products of its action on the wall polysaccharides xyloglucan and cellulose, provide a complex regulatory system, acting at three or possibly four different levels. Our recent observations will be presented in terms of the following speculations. (1) SPECULATION: Low levels of auxin activate cellulase (by inducing H(+)-secretion?), which cuts inter-microfibrillar xyloglucan chains, loosening the cell wall and tending to promote growth. OBSERVATION: auxins induce xyloglucan turnover and decrease the mean Mr of wall xyloglucan. Re-incorporation of xyloglucan fragments suggests that transglycosylation predominates over hydrolysis. (2) SPECULATION: Moderate levels of auxin activate cellulase further; the enzyme generates small amounts (nM) of oligosaccharides, some of which are growth-inhibitory. This process tends to moderate growth. OBSERVATION: Xyloglucan nonasaccharide (XG9-see Fig. 2) at 1-10 nM antagonises auxin-induced growth. The effect is seen with fucose-containing oligosaccharides (XG9, XG5, fucosyl-lactose), but not with XG7 or XG8. XG9 (1 nM) and XG10 (0.1 nM) and cellohexaose (10 nM) also block H(+)-induced growth. (3) SPECULATION: Higher levels of auxin induce cellulase synthesis leading to the generation of higher concentrations of oligosaccharides that can mimic auxin. This process thus tends to restore growth. OBSERVATION: all xyloglucan-oligosaccharides tested (HPLC-pure XG7, XG8, XG9, XG9n - Fig. 2) promote growth at 1 microM, the order of effectiveness being XG9n greater than XG8 greater than XG7 conquent to XG9. The same oligosaccharides (at 1-100 microM) promote the mid-chain hydrolysis of xyloglucan by plant cellulase, while slightly inhibiting total hydrolysis. The order of effectiveness is XG9n congruent to XG8 greater than XG7 congruent to XG9. The promotion of mid-chain hydrolysis (and/or transglycosylation) might be expected to be particularly effective at loosening the cell wall: most of the wall's xyloglucan molecules might suffer a single cleavage rather than a few of them undergoing complete degradation. (4) SPECULATION: Very high levels of auxin induce excessive levels of cellulase, and therefore of oligosaccharides. This inhibits growth. OBSERVATION: XG7, XG9 and XG9n lose their auxin-like activity at 10 microM.

Cell Membrane↗
PubMed1989

Validity of urinary urea nitrogen as a measure of total urinary nitrogen in adult patients requiring parenteral nutrition.

The validity of the urinary urea nitrogen (UUN) estimate of total urinary nitrogen (TUN) was tested in patients who required iv nutrition. UUN and TUN were determined in 120 urine collections from ten preoperative, 13 postoperative, and 11 stressed patients. The relationship between TUN and UUN was examined by linear regression, and analysis of covariance was used on log-transformed data to assess differences between the patient groups. Although there was a close relationship between UUN and TUN for the preoperative patients (r2 = .94, total range of differences = 3.85 g N), this was not as accurate in postoperative and stressed patients (r2 = .69 and .76, respectively, total range of differences = 16.8 and 10.7 g N, respectively). There was no significant difference between the slopes of the regression lines for the relationship between UUN and TUN for three groups (f = 1.1, df = 2114, p less than .3), but the intercepts of the regression lines differed between the preoperative and stressed patient groups (t = 3.47, v = 114, p less than .001). The relationship between TUN and UUN for the whole group was improved by the inclusion of the independent variables of both the patient's clinical state and the urinary creatinine excretion. Arm muscle circumference, which is an estimate of muscle mass, may replace creatinine excretion with little loss in prediction accuracy.

Adult↗
PubMed1989

Major pancreatic resections.

A personal series of 50 major pancreatic resections has been reviewed to assess some issues of the operative decision in relation to a patient's expected outcome. An accurate histological diagnosis was not always available at the time of operation. At operation, 25 were thought to have invasive carcinoma of the pancreas and 14 to have ampullary carcinoma but the final histology demonstrated these diagnoses as accurate in 21 and 12 cases, respectively. The remaining 17 patients had a variety of histological findings which necessitated resection. Thirty-eight per cent of patients had major postoperative morbidity resulting in a median postoperative stay of 21 days after a Whipple procedure and 28 days after total pancreatectomy. The perioperative mortality rate was 6%. The median survival was 12 months for patients with invasive pancreatic carcinoma, 37 months for patients with ampullary carcinoma and 19 months for the whole group; the 5-year survival results were 13%, 40% and 25%, respectively. It is concluded that surgical resection of small pancreatic tumours is justified because some patients gain long-term survival with an acceptable risk of perioperative mortality and because the exact diagnosis may not be established at the time of surgery.

Adenocarcinoma↗
PubMed1988

Expression of a histone H1-like protein is restricted to early Xenopus development.

Genes whose expression is restricted to oogenesis and early development may have important functions in these processes. Northern analysis showed that Xenopus B4 mRNA is expressed in oogenesis and embryogenesis through to the neurula stage. Immunocytochemistry with anti-B4 antibodies showed that B4 protein is only detectable in preneurula stages; it is localized to nuclei and is associated with metaphase chromosomes. Immunoblotting revealed approximately constant levels of B4 protein per embryo for the first 2 days of development. Thus, as the number of nuclei increases during early development, the amount of B4 protein per nucleus is diluted out. Sequencing of two B4 cDNA clones revealed that the predicted B4 translation product is a 29-kD protein with 29% identity with histone H1, distributed over the entire length of its sequence. The B4 protein also has certain other H1 protein characteristics--a tripartite structure consisting of a mainly hydrophobic central domain flanked by an amino-terminal segment and a long hydrophilic carboxyterminal tail containing a tandemly repeated amino acid motif. However, in contrast to histone H1 mRNA, B4 mRNA has a classic polyadenylation signal, is polyadenylated, and lacks the histone H1 3' noncoding consensus sequence involved in RNA processing.

Amino Acid Sequence↗
PubMed1988

Destruction of a translationally controlled mRNA in Xenopus oocytes delays progesterone-induced maturation.

The maternal mRNA D7 is a moderately abundant transcript in Xenopus laevis whose expression is highest in, and perhaps restricted to, oogenesis and early embryogenesis. The nucleotide sequence of cloned D7 cDNA was determined and shown to have the capacity to code for a 31-kD protein. This amino acid sequence was searched against a protein data base, and no homologous proteins were found. Antibodies directed against D7 recognize in Xenopus embryos a soluble, cytoplasmic protein with an apparent molecular weight on SDS gels of 36,000. The D7 protein is absent from oocytes and first begins to accumulate during oocyte maturation. Its levels are highest during the first day of embryonic development and then decrease; D7 protein was not detected in adult tissues. D7 mRNA was selectively destroyed by injection into oocytes of antisense oligodeoxynucleotides. Analysis of injected oocytes by Northern and Western blotting showed site-specific cleavage and subsequent degradation of the D7 mRNA and the failure of the D7 protein to accumulate during progesterone-induced maturation. The loss of D7 protein affects the maturation process itself, significantly delaying the time course of germinal vesicle breakdown. Thus, D7 is a newly described protein involved in oocyte maturation.

Amino Acid Sequence↗
PubMed1988

Serum concentrations of oestradiol and progesterone, and sexual behaviour during the normal oestrous cycle in the leopard (Panthera pardus).

Three mature nulliparous female leopards were studied for 5 years. During three separate 6-month periods serum oestradiol and progesterone concentrations were measured at weekly intervals. Oestradiol was elevated over 21 pg/ml for 54 weeks during these 3 periods, and 36 oestradiol peaks (65.8 +/- 6.3 pg/ml (mean +/- s.e.m.), range 21-172 pg/ml) were identified. Daily frequency of feline reproductive behaviours averaged over each week increased from 1.9 +/- 0.2 (n = 93) during weeks with low serum oestradiol concentrations (less than 21 pg/ml) to 5.3 +/- 0.6 (n = 54) during weeks when serum oestradiol concentrations (greater than 21 pg/ml) were high. Increased serum progesterone concentrations (13-98 n/gml) were observed on 5 occasions in 2 leopards housed together. These presumptive luteal phases lasted from 1 to 5 weeks. Baseline progesterone values were 1.6 +/- 0.4 ng/ml (n = 131). No progesterone increments were observed in isolated animals, and serum concentrations remained at baseline levels. These limited observations suggest that female leopards do not require intromission to induce ovulation and luteal function. The average interval between oestradiol peaks for cycles with no progesterone increment was 3.4 weeks (range 1-6 weeks). The interval for the 3 complete cycles associated with elevated progesterone concentrations was 7.3 weeks. Analysis of sexual behaviours over the 5-year study period revealed no evidence of seasonality in these captive leopards.

Animals↗
PubMed1988

Hemolysis of chicken erythrocytes by t-butyl hydroperoxide and protection by plasma.

Chicken erythrocytes treated with 100-microM t-butyl hydroperoxide (t-BHP) were more than 80% hemolyzed in 2 h and more than 90% hemolyzed after 4 h of incubation. Autologous plasma retarded the rate of hemolysis of chicken red cells produced by t-BHP. Dialysis of chicken plasma resulted in a marked decrease in the ability of plasma to protect erythrocytes from hemolysis by t-BHP. Low molecular weight components of plasma such as uric acid are hypothesized to account for much of the dialyzable material that protects red cells from hemolysis.

Animals↗
PubMed1988

Cortisol responses to cholinergic drugs in Alzheimer's disease.

Patients with Alzheimer's disease participated in a trial of two sessions in which they received physostigmine and neostigmine in a double-blind crossover design. Most of these patients subsequently participated in a scopolamine vs saline double-blind crossover trial using a similar design. Physostigmine increased plasma cortisol relative to neostigmine, with the greatest difference at time points greater than 90 min post drug oral administration. Physostigmine also significantly decreased plasma cholinesterase (ChE). There was a significant positive correlation between the effects of physostigmine on increasing cortisol and decreasing ChE; there was no correlation between the increase in cortisol of cholinesterase inhibitor following neostigmine administration, but neither of these chemical parameters is related to the drug's effects on cognitive functioning.

Aged↗
PubMed1988

Operative cholangiography using a modified disposable vascular clip.

After frequent use of this modified disposable clip, obtaining cholangiograms has been both easy and quick while minimizing trauma to the tissues of the cystic duct. The clip can be used safely through any incision, small or large, and it is a good tool in facilitating the interoperative cholangiogram.

Catheterization↗
PubMed1987

Polymerization of vertebrate non-muscle and smooth muscle myosins.

We investigated how light chain phosphorylation controls the stability of filaments of vertebrate non-muscle myosins (from bovine thymocytes and chicken intestine epithelial brush border cells) and smooth muscle myosin (from chicken gizzard) in vitro. Using a sedimentation assay, the solubilities of the myosins were determined by measuring the amounts of myosin monomers (Cm) and filaments (Cp) present under a given set of conditions as a function of the total myosin concentration (Ct). Below 200 mM-NaCl, each myosin displayed distinct "critical monomer concentrations" (Cc) for polymerization, which were dependent on the salt concentration, the state of light chain phosphorylation and the presence of MgATP. At 150 mM-NaCl, MgATP increased the Cc of non-phosphorylated brush border myosin approximately five to tenfold, thymus myosin approximately 10 to 15-fold, and gizzard myosin approximately 25 to 50-fold. When these myosins were phosphorylated, MgATP had little effect on their solubilities, and their Cc values remained low. Analytical ultracentrifugation and electron microscopy demonstrated that the myosins were present in three different conformational states under the conditions used in the sedimentation assays, i.e. filaments, extended monomer (6 S) and folded monomer (10 S). Since at equilibrium only filaments and monomers were observed, we suggest that the polymerization pathway for these myosins can be analysed in terms of a dynamic monomer-polymer equilibrium (polymer in equilibrium 6 S monomer in equilibrium 10 S monomer). At roughly physiological ionic strength, light chain dephosphorylation (in the presence of MgATP) promotes the folded state (10 S), whereas phosphorylation promotes the extended state (6 S), and thereby favours filament assembly. The relevance of the monomer-polymer equilibrium to the state of organization of the myosin in vivo is discussed.

Animals↗