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Biomedical subjects

S J Miller

Publications and source records attributed to S J Miller.

At least 109 records · Page 6Linked to original sources
PubMed1989

Phosphorylation and degradation of HMG CoA reductase.

3-Hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase is the limiting enzyme step in cholesterol formation in mammalian liver and other tissues. It is a glycoprotein of 97,000 daltons embedded in the endoplasmic reticulum with a long cytoplasmic extension that is the site of catalytic conversion of HMG CoA to mevalonate. The enzyme is subject to both long-term (induction/repression; degradation) and short-term control (reversible phosphorylation) mediated by endocrine signaling (insulin, glucagon) and through negative feedback by metabolic products of mevalonate (e.g., cholesterol). The catalytic capacity of microsomal reductase falls rapidly in the presence of several protein kinases (reductase kinase, protein kinase-C, calmodulin-dependent protein kinase). Activity is restored with various protein phosphatases. Increased phosphorylation of reductase in intact cells after addition of glucagon or mevalonate is followed by enhanced degradation of the enzyme. In an in vitro model system, phosphorylated, native microsomal reductase is more rapidly cleaved by the calcium-dependent, neutral protease calpain than the dephosphorylated from of reductase. Our present research which centers on the mechanism of the in vitro model system is reviewed. Calpain in the presence of Ca2+ cleaves the cytosolic domain of phosphorylated 97 kDa reductase at two points giving rise to two fragments of nearly the same size that appear as a 52-56,000 dalton doublet by electrophoresis and immunoblotting. In the same system native reductase labeled with [gamma-32P]ATP generates a doublet with 32P solely in the upper (heavier) band. This indicates that serine phosphorylation sites lie between the two calpain cleavage loci. These are positioned in the "linker" region of the long carboxy-terminal cytosolic domain near the membrane. This segment possesses five invariant serine residues and two PEST sequences (constellations of proline, glutamate, serine and threonine) that are characteristic of proteins with short half-lives. If phosphorylation of HMG CoA reductase is confined to the linker region, we must look to this domain in order to interpret the resulting conformational changes that markedly influence reductase catalytic activity and prepare the enzyme for degradation.

Adenosine Triphosphate↗
PubMed1989

Nutritional deficiency and the skin.

Cutaneous changes occur in deficiency states of many nutritional elements: ascorbic acid, retinol, protein-energy, cyanocobalamin, phytonadione (vitamin K), biotin, ribroflavin, pyridoxine, niacin, essential fatty acids, and zinc. There are also inherited disorders of copper, biotin, zinc, and tryptophan metabolism. Cutaneous vitamin D synthesis is inhibited by sunscreen use. The striking skin changes of the glucagonoma syndrome may be related to nutritional pathways.

Deficiency Diseases↗
PubMed1989

Antimicrobial activity of stratum corneum lipids from normal and essential fatty acid-deficient mice.

Among the cutaneous effects of an essential fatty acid deficient (EFAD) diet are hyperdesquamation, increased transepidermal water loss (TEWL), and altered lipid profiles, characteristics also common to inflammatory dermatoses. Because fatty acids are antimicrobial, we examined the indigenous skin flora of normal and EFAD hairless mice, and compared the antimicrobial efficacy of lipids extracted from their stratum corneum. EFAD mice supported 100-fold more bacteria than normal mice, and were the only group from which Staphylococcus aureus were routinely isolated. Despite this greater carriage, in vitro experiments demonstrated that EFAD lipids are more lethal than normal lipids against Streptococcus pyogenes, S. aureus, S. epidermidis, Micrococcus sp., and a coryneform. Skin fungi were equally susceptible to both extracts. After thin layer chromatography, the most active fractions were found to be glycosphingolipids and phospholipids. EFAD extracts had 35% more free fatty acids and 75% more glycosphingolipids; normal extracts had more triglycerides and phospholipids. S. aureus strain 502A survived equally well on EFAD as on normal mice. Normal lipids applied on EFAD mice had no additional effect, but EFAD lipids on normal mice brought about a 35% reduction of the inoculated bacteria. If the mice were pretreated with alcohol, carriage of strain 502A was reduced by 71%. If instead the mice were previously washed with acetone to increase TEWL, a 97% reduction of the staphylococcus occurred. The application of normal flora to such acetone-washed mice decreased the efficacy to 76%. EFAD and normal lipids on human subjects were equally ineffective in eliminating strain 502A.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Monoclonal antibodies reacting with serogroup and serovar specific epitopes on different lipopolysaccharide subunits of Leptospira interrogans serovar pomona.

Monoclonal antibodies with two kinds of specificities, produced against Leptospira interrogans serovar pomona, were studied by agglutination and immunoblotting. Antibodies reacted either exclusively with serovar pomona or with all members of the Pomona serogroup, but none of the antibodies reacted with representative serovars of other serogroups. Both antibodies recognized epitopes on purified lipopolysaccharide (LPS) from serovar pomona. In immunoblotting experiments the serogroup specific antibody recognized both the major LPS bands of 21 kDa and 26 kDa whereas the serovar specific antibodies reacted only with the 26 kDa band, thus localizing serovar specificity in the 26 kDa band and serogroup specific epitopes on at least two different LPS subunits.

Animals↗
PubMed1989

Influence of duodenal digesta composition on abomasal outflow, motility and small intestinal transit time in sheep.

1. A study was made of the influence of duodenal infusion of some of the components of the digesta on gastrointestinal motility, abomasal outflow and small intestinal transit time in seven sheep fed 1500 g grass pellets/day. Gastrointestinal motility was recorded by electromyography. Abomasal outflow was estimated according to the rate of dilution of CrEDTA injected and sampled via an abomasal catheter. Small intestinal transit time was measured by the passage of Phenol Red from the duodenum to the terminal ileum. 2. Abomasal outflow was inhibited during 3 h infusions (5 ml/min) of 100 mM-acetic, propionic, butyric and lactic acids, of 50 mM-HCl, of 0.56 M-glucose, and of 2 and 4% protein hydrolysate. Abomasal motility was inhibited by these infusions and by infusion of 234 mM-oleic acid (0.75 ml/min), of a fat emulsion (Intralipid 20% 0.3 ml/min) and of 50 mM-L-tryptophan (7.5 ml/min). 3. Abomasal motility and, where tested, abomasal outflow, were not affected by duodenal infusion of 150 mM-NaHCO3 (5-10 ml/min), 0.28 M-NaC1 (5-7.5 ml/min), distilled water (5-7.5 ml/min), 25 mM-L-tyrosine (5 ml/min), and of 50 mM-acetic, propionic, butyric and lactic acids (5 ml/min). 4. At concentrations or rates of infusion above the threshold dose needed to inhibit abomasal motility, small intestinal motility was altered and the frequency and amplitude of the reticulo-ruminal contractions were inhibited. 5. The transit time through the small intestine was increased during infusion of 100 mM-acetic, propionic, butyric and lactic acids and decreased during infusion of 0.56 M-glucose and Intralipid. 6. Inhibition of abomasal motility and outflow in sheep receiving 1500 g/day grass pellets was calculated to require increases in the duodenal concentration of volatile fatty acids of about 150% and K+ of about 38%, and to require an increase in the rate of delivery to the duodenum of H+ of about 90%, nitrogen of about 22% glucose of about 2000% and fat of about 84%. 7. These findings are discussed in relation to the composition of abomasal and duodenal digesta in sheep fed different diets. 8. It seems likely that components of duodenal chyme, such as H+, volatile fatty acids, glucose and fat only affect abomasal outflow in sheep fed high-grain diets (glucose, volatile fatty acids), or diets highly supplemented with fat (fat), for short periods after meal feeding (volatile fatty acids) or under abnormal conditions (H+).(ABSTRACT TRUNCATED AT 400 WORDS)

Abomasum↗
PubMed1989

Influence of breed and diet on growth, nutrient digestibility, body composition and plasma hormones of Brangus and Angus steers.

Two split-plot designed experiments were conducted to determine the effects of breed (Angus, A, or Brangus, B) and diet (fescue hay, FH; corn silage, CS; or concentrate) on composition and rate of growth, diet digestibility and plasma hormones of steers. In Exp. 1, 10 steers (five of each breed) were fed a CS-based diet followed by a FH-based diet for two consecutive 60-d periods. Both breeds had lower (P less than .01) DM intake and digestibility when fed FH than when fed CS diets. The B steers had higher (P less than .01) plasma insulin concentrations than A steers when fed the CS diet. In Exp. 2, during two consecutive years, 10 steers previously fed CS- and FH-based diets were finished with a corn silage-whole shelled corn-based diet. During yr 1, A steers had higher (P less than .01) DM intake and plasma triiodothyronine (T3) and thyroxine (T4) concentrations (P less than .05) than B steers did. Although final weights were similar (P greater than .10), A steers had heavier (P less than .05) carcass weights than B steers did. During yr 2, A steers had higher (P less than .07) DM and starch digestibilities and higher (P less than .01) plasma T4 concentrations than B steers did. The greater (P less than .01) energetic efficiency of A steers was attributed to the greater rates of fat deposition during yr 2. Regardless of type of diet fed, A steers were more efficient at depositing energy. Higher circulating T4 concentrations of A than B steers may explain some of the physiological differences between these breeds.

Animal Feed↗
PubMed1988

In vitro and in vivo antistaphylococcal activity of human stratum corneum lipids.

Despite the assumption that sebum-derived fatty acids are responsible for cutaneous antimicrobial defense, no studies have assessed the contribution of epidermis-derived lipids. Herein, we tested the antistaphylococcal effects of human stratum corneum lipids, enriched in endogenous, keratinocyte-derived species obtained by lipid extraction and thin-layer chromatography, for antimicrobial activity in both in vitro and in vivo systems. Whereas the most potent species in vitro were the free fatty acids, polar lipids and glycosphingolipids also demonstrated antistaphylococcal activity in vitro, while other neutral lipids displayed virtually none, results that were confirmed with authentic standards in vitro. In a pilot study on delipidized forearm test sites in human volunteers, naturally occurring free fatty acids, polar lipids, and glycosphingolipids exhibited significantly more antistaphylococcal activity than other stratum corneum lipids or vehicle controls. Finally, biopsy specimens of incubated skin sites demonstrated penetration of staphylococci through lipid-enriched intercellular domains. These results provide the first evidence that endogenous, epidermis-derived skin lipids may contribute to cutaneous antimicrobial resistance.

Fatty Acids, Nonesterified↗
PubMed1988

Streptococcus mutans endocarditis: report of three cases and review of the literature.

Our findings indicate that S. mutans endocarditis is capable of causing significant morbidity and mortality, as exemplified by the prolonged and complicated hospital course of our patients and the ultimate death of one of them. S. mutans endocarditis is probably underreported because most clinical laboratories do not speciate the viridans streptococci. Isolates of S. mutans should be tested for tolerance that would require the addition of an aminoglycoside to the penicillin regimen. Our experience agrees with the literature and indicates that S. mutans is primarily a pathogen in elderly patients with heart disease and may be associated with IHSS.

Age Factors↗
PubMed1988

Cutaneous cryptococcus resembling molluscum contagiosum in a patient with acquired immunodeficiency syndrome.

A hemophiliac man who tested positive for the human immunodeficiency virus presented with facial lesions resembling molluscum contagiosum as the initial manifestation of systemic cryptococcal infection. Widespread molluscum contagiosum is being seen with increasing frequency in patients who have been exposed to the human immunodeficiency virus, and examination of biopsy specimens to rule out atypical fungal infection is mandatory.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Influence of frame size and zeranol on growth, compositional growth and plasma hormone characteristics.

A 2 X 2 factorially arranged trial was conducted to compare effects of implant (zeranol) and frame size on weight and compositional gain, and plasma hormone concentrations. Angus, Charolais X Hereford and Hereford X Angus yearling steers (34 steers averaging 270 kg body weight) were randomly assigned to treatments of small (SF) vs large frame (LF) and implant (I) vs no implant (NI). Steers were implanted at 0 and 97 d and individually fed an 81% whole shelled corn and 11.5% corn silage-based diet (dry basis) for a 175-d period. Shrunk weights and body measurements for frame size determination were taken initially and at approximately 28-d intervals; blood was collected via venipuncture at 14-d intervals for analyses of insulin (IN), triiodothyronine (T3), thyroxine (T4) and glucose concentrations. Steers were also counted in a whole body counter for measurement of 40K content and prediction of whole body protein and fat. The I steers showed an improvement (P less than .05) in daily gain regardless of frame size for the total trial. The I LF steers required 18% more dry matter to attain higher daily gain for 97 to 175 d; I steers were more efficient (P less than .05) at converting dry matter to gain during 0 to 97 d and 0 to 175 d. Daily fat deposition was increased (P less than .05) in I steers, while protein deposition was not affected by I. Plasma IN concentrations were numerically elevated (P less than .10) in I steers regardless of frame size, during the initial 97 d. Implant did not influence (P greater than .10) plasma T3, T4 and glucose concentrations regardless of frame size. Steers responded differently to zeranol implant over time regarding plasma T4 concentrations (P less than .003). Steers differing in frame size responded similarly in rate of gain, in feed conversion and in patterns of plasma insulin concentrations to zeranol implants.

Animals↗
PubMed1986

Phosphorylation state of HMG CoA reductase affects its catalytic activity and degradation.

The expressed catalytic activity of liver microsomal HMG CoA reductase, the limiting enzyme in cholesterol synthesis, is reversibly diminished by phosphorylation in vitro. In intact hepatocytes the expressed activity of HMG CoA reductase is enhanced by incubation of cells with insulin, and diminished by treatment with glucagon or with mevalonate. In the latter situations the level of total reductase activity falls following initial inactivation (phosphorylation) of the enzyme. This observation suggested that the phosphorylated form of HMG CoA reductase is more sensitive to proteolysis. HMG CoA reductase is a 97,000 dalton (97 K) integral protein of the endoplasmic reticulum with a cytosolic domain that includes the catalytic site and serine residues that may be reversibly phosphorylated. In vitro the Ca2+-activated proteolytic enzyme, calpain, generates two catalytically-active fragments: a membrane bound 62 K and a soluble 53 K form of the enzyme which are quantified by specific immunoblot procedures. Cleavage of the native 97 K HMG CoA reductase is enhanced by pretreatment (inactivation) of microsomes with ATP (Mg2+) and liver reductase kinase compared to microsomes pretreated with protein phosphatase. This is reflected in a loss of 97 K reductase and an increase in the soluble 53 K form of the enzyme. Degradation of HMG CoA reductase in hepatocytes is partially blocked by lysosomotropic agents and insulin. A steady state model for the turnover of proteins subject to reversible phosphorylation has been developed which recognizes fractional degradative rate constants for the phosphorylated and dephosphorylated species.

Animals↗
PubMed1986

The art of making an incision.

Successful surgery begins with accurate placement and proper execution of the skin incision. It is the first step toward satisfactory scar formation. Knowledge of the skin mechanics as well as circulation, local anatomy, and wound healing are the tools necessary for accurate violation of the skin. Langer's cleavage lines have given way to "relaxed skin tension lines."

Collagen↗
PubMed1986

The bilobed skin flap rotation.

The bilateral rotational skin flap is a plastic surgical technique suitable for filling defects on the foot too large to be served by a single pedicle flap. The execution of such a procedure requires careful planning and evaluation for sufficient circulatory support. Consideration for weight bearing is essential. No such flap rotations should be undertaken without a full understanding and acceptance of the consequences of failure, both on the part of the patient as well as the surgeon.

Foot Diseases↗
PubMed1986

The diagnosis and treatment of infections of the pedal integument.

Dr. Miller's discussion of the diagnosis and management of soft tissue infections is probably one of the most important topics in this issue. We are all faced with the potential for relatively minor infections becoming serious problems. Having a sound understanding of the infectious process and treatment regimens is extremely important in our general practices. Few things can make a patient as unhappy or destroy good surgical results as quickly and easily as an infection. I recommend reading the articles suggested by Dr. Miller and add that I believe that if the infection has not responded as quickly to therapy as is expected, an infectious disease consultation should be requested.

Adult↗