Isolation and identification of a diuretic hormone from the mealworm Tenebrio molitor

A diuretic hormone of unusual structure was isolated from extracts of whole heads of the mealworm Tenebrio molitor. The hormone is a 37-aa peptide of 4371 Da, with the sequence SPTISITAPIDVLRKTWEQERARKQMVKNREFLNSLN. This peptide increases cAMP production in Malpighian tubules of T. molitor. The amino acid sequence reveals that this peptide is a member of the family of sauvagine/corticotropin-releasing factor/urotensin I-related insect diuretic hormones. The C-terminal sequence of this peptide is quite different from other members of this family, which have a hydrophobic C terminus (isoleucinamide or valinamide). When aligned comparably, T. molitor diuretic hormone has a more hydrophilic C terminus, leucylasparagine (free acid). In contrast to all other known diuretic hormones of this family, this peptide has exceptionally low stimulatory activity on cAMP production in Malpighian tubules of Manduca sexta. However, at nanomolar concentrations it stimulates cAMP production in Malpighian tubules of T. molitor. Diuretic hormones of this family have been isolated previously from Lepidoptera, Orthoptera, Dictyoptera, and Diptera. This appears to be the first diuretic hormone isolated from a coleopteran insect.

A designed heterotrimeric coiled coil

Principles that guide folding of coiled coils were tested by designing three peptides that preferentially associate with each other to form a heterotrimeric coiled coil. The core positions of the designed helices contained residues that promote formation of trimeric coiled coils. Ionic interactions were employed to mediate heterospecificity, and negative design was used to favor formation of the heterotrimer over alternative arrangements. A program was written to select sequences that maximized the number of attractive interhelical interactions in a parallel heterotrimer and the number of repulsive electrostatic interactions in alternative species. Solution studies indicate that an equimolar mixture of the three peptides forms a helical trimer with high specificity and stability. These results validate the principles used to guide the design and suggest that the heterotrimer may serve as a useful, autonomous trimerization domain.

Mass spectrometric determination of the radical scission site in the anaerobic ribonucleotide reductase of Escherichia coli

Active anaerobic ribonucleotide reductase from Escherichia coli contains an oxygen sensitive organic radical, proposed to reside on glycine-681 at the C-terminal end of the polypeptide chain. Exposure of the radical containing enzyme to oxygen results in cleavage of the molecule at the site of the hypothetical radical. We determined by mass spectrometry the size of the complete and the C-terminal-processed polypeptides. The difference in size between the two molecules shows that cleavage occurs at the N-terminal side of glycine-681, demonstrating that the organic radical is indeed located on this amino acid residue.

Time course for exercise-induced alterations in insulin action and glucose tolerance in middle-aged people

The purposes of this study were 1) to investigate glucose tolerance and insulin action immediately after exercise and 2) to determine how long the improved glucose homeostatic mechanisms observed 12-16 h after exercise persist. Nine (seven men, two women) moderately trained middle-aged (51 +/- 3 yr) subjects performed 45 min of exercise at 73 +/- 2% of peak O2 uptake for 5 days, followed by 7 days of inactivity. Oral glucose tolerance tests (OGTT; 75 g) were performed immediately postexercise (IPE; approximately 30 min) after the final exercise bout and 1, 3, 5, and 7 days after exercise. The incremental area under the plasma glucose curve was markedly higher IPE (355 +/- 82 mM.min) compared with those on days 1 (136 +/- 57 mM.min; P < 0.05) and 3 (173 +/- 62 mM.min; P < 0.05). The glucose area was significantly higher on days 5 (213 +/- 80 mM.min) and 7 (225 +/- 84 mM.min) compared with those on days 1 and 3 (P < 0.05). The incremental insulin area IPE (3,729 +/- 1,104 microU.ml-1.min) was 43% higher compared with that on day 1 (2,603 +/- 635 microU.ml-1.min; P < 0.05) and 66% higher compared with that on day 3 (2,240 +/- 517 microU.ml-1.min; P < 0.05). The insulin area increased to 3,616 +/- 617 microU.ml-1.min after 5 days of inactivity (P < 0.05). An additional 48 h of inactivity did not result in any further increase in the plasma insulin response.(ABSTRACT TRUNCATED AT 250 WORDS)

Insertion of a coiled-coil peptide from influenza virus hemagglutinin into membranes

The trimeric protein hemagglutinin (HA) of the influenza viral envelope is essential for cell entry. To investigate the interaction of HA with membranes, two 40-residue, cysteine-substituted peptides comprising the loop region and the first part of the coiled-coil stem were synthesized and modified with a nitroxide spin label. Electron paramagnetic resonance analysis revealed that the peptide inserts reversibly into phospholipid vesicles under endosomal pH conditions. This result suggests that some or all of the long coiled-coil trimer of HA may insert into membranes, which could bring the viral and cell membranes closer together and facilitate fusion.

Molecular and genetic characterization of GABP beta

This report outlines three observations relating to GABP beta, a polypeptide constituent of the heterotetrameric transcription factor GABP. Evidence is presented showing that the mouse genome encodes two highly related GABP beta polypeptides, designated GABP beta 1-1 and GABP beta 2-1. Genomic and cDNA copies of the newly defined Gabpb2 gene were cloned and characterized, providing the conceptually translated amino acid sequence of GABP beta 2-1. The genes encoding these two proteins, as well as GABP alpha, were mapped to three unlinked chromosomal loci. Although physically unlinked, the patterns of expression of the three genes were strikingly concordant. Finally, the molecular basis of GABP beta dimerization was resolved. Carboxy-terminal regions of the two GABP beta polypeptides, which mediate dimerization, bear highly related primary amino acid sequences. Both sequences are free of alpha-helix destabilizing residues and, when displayed on idealized alpha-helical projections, reveal marked amphipathy. Two observations indicate that these regions adopt an alpha-helical conformation and intertwine as coiled-coils. First, the dimer-forming region of GABP beta 2-1 can functionally replace the leucine zipper of a bZIP transcription factor. Second, a synthetic peptide corresponding to this region shows distinctive helical properties when examined by circular dichroism spectroscopy. Finally, evidence is presented showing that GABP beta 1-1 and GABP beta 2-1 can heterodimerize through this carboxy-terminal domain, but neither protein can heterodimerize via the dimer-forming region of the bZIP protein C/EBP beta.

Effect of endurance training on plasma free fatty acid turnover and oxidation during exercise

Plasma free fatty acid (FFA) levels tend to be lower and the plasma lipolytic hormone response to prolonged exercise of the same intensity is blunted after endurance exercise training. To determine whether training elicits a corresponding decrease in plasma FFA turnover and metabolism during prolonged exercise, we measured plasma [1-13C]palmitate kinetics and oxidation and respiratory gas exchange in 13 subjects during the latter portion of a 90- to 120-min bout of cycle ergometer work performed before and after 12 wk of alternate-day cycling and running. Training increased total fat oxidation during prolonged exercise by 41% (P < 0.005). However, for the final 30-60 min of the cycle ergometer protocol, the rate of 13CO2 production from [1-13C]palmitate oxidation was 27% lower (P < 0.05), the rate of palmitate turnover was 33% less (P < 0.05), and plasma FFA and glycerol concentrations were 32 and 20% lower (P < 0.05), respectively, than in the untrained state. Thus endurance exercise training results in decreased plasma FFA turnover and oxidation during a 90- to 120-min bout of submaximal exercise because of a slower rate of FFA release from adipose tissue.

Effects of eccentric exercise on insulin secretion and action in humans

The effects of an exhaustive bout of eccentric exercise on insulin secretion and action were determined using the hyperglycemic clamp technique. Clamps were performed on eight healthy men after 7 days of inactivity and approximately 36 h after a bout of eccentric exercise. Eccentric exercise consisted of 10 sets of 10 repetitions of combined knee extensions and flexions for each leg at a mean torque 84 +/- 5% of peak concentric torque. During the hyperglycemic clamp procedure, plasma glucose concentration was acutely raised to 10 mmol/l and was maintained near this level for 120 min. Arterialized blood samples were obtained from a heated hand vein to determine plasma glucose and insulin concentrations. Eccentric exercise appeared to produce marked muscle damage, as indicated by a 50-fold increase in plasma creatine phosphokinase (100 +/- 17 vs. 5,209 +/- 3,811 U/l, P < 0.001) and subjective reports of muscle soreness. Peak insulin response during the early phase (0-10 min) of the hyperglycemic clamp was higher after eccentric exercise (183 +/- 38 microU/ml) than after the control clamp (100 +/- 23 microU/ml, P < 0.005). Late-phase (10- to 120-min) insulin response was not altered after eccentric exercise. Peak plasma C-peptide concentrations were higher during the early phase (5.0 +/- 0.7 vs. 4.3 +/- 0.8 ng/ml, P < 0.05) and the late phase (7.5 +/- 0.9 vs. 5.4 +/- 0.6 ng/ml, P < 0.05). Prior eccentric exercise had no significant effect on whole body glucose disposal or glucose disposal rate adjusted for prevailing plasma insulin concentration. These data provide evidence that a single bout of eccentric exercise causes an increase in pancreatic beta-cell insulin secretion in response to hyperglycemia.

Mass spectrometric analysis of the fragments produced by cleavage and reduction of rat prolactin: evidence that the cleaving enzyme is cathepsin D

The site(s) at which mammary tissue enzymatically cleaves rat (r) PRL, and the possibility that the cleaving activity is cathepsin D, were investigated using mass spectrometry and enzyme inhibitors. Cleavage of intact rPRL [22,566 atomic mass units (amu)] by either mammary gland-conditioned medium or cathepsin D (both at pH 3) reduced the mass of the molecule by 397 amu. Subsequent reduction of the large rPRL fragment cleaved by either method generated two fragments of 16,364 and 5808 amu. The mass of the smaller fragment is consistent with the report of Vick et al. (Biochim Biophys Acta 931: 196-204, 1987) that its amino-terminal residue is Ser149. These results indicate that both enzyme preparations cleave rPRL by excision of the tripeptide Leu-Val-Trp (mass = 397 amu) between residues 145 and 149. The ability of both enzyme preparations to cleave rPRL at pH3 was inhibited by pepstatin A but not by phenylmethane sulfonyl fluoride, and both preparations were essentially inactive at pH7. Accordingly, the PRL-cleaving activity of rat mammary tissue is probably cathepsin D.

Relationship between glucose tolerance and glucose-stimulated insulin response in 65-year-olds

BACKGROUND

Decreased insulin secretion may contribute to the deterioration of glucose tolerance associated with aging.

METHODS

We studied the insulin response to a 3-hour hyperglycemic clamp (10 mM) of 19 young (24 +/- 1 y) subjects with normal glucose tolerance and 60 older (65 +/- 1 y) subjects with various levels of glucose tolerance.

RESULTS

The noninsulin dependent diabetic (NIDDM) group had a diminished first phase immunoreactive (IR)-insulin response compared to young and nondiabetic older groups (p < .05). The older groups had a lower rate of change in IR insulin concentration during the third hour of hyperglycemia compared to the young group (p < .05). This was not, however, a universal finding, because a decreased third hour response was not seen in a subgroup of older subjects whose glucose tolerance was similar to that of the young group. Another subgroup of older subjects with a decrease in glucose tolerance mild enough to be considered normal by the National Diabetes Group Criteria tended to have both an increase in the early insulin response and a decrease in the third hour response. More severe decreases in glucose tolerance were associated with blunting of the early response.

CONCLUSION

Aberrations in early and late phase glucose-stimulated insulin responses appear to be present in older subjects with even mildly decreased glucose tolerance. Some individuals, however, show no evidence of deterioration of glucose tolerance or insulin response to glucose with aging, at least up to age 70 years.

Polysymptomatic syndromes and autonomic reactivity to nonfood stressors in individuals with self-reported adverse food reactions

This study compared symptom reports and cardiovascular reactivity of a group of 24 individuals recruited from the community who reported a cognitive or emotional symptom caused by at least one food (food-sensitivity reporters, FSR) vs those of 15 controls (C) without a history of food, chemical, drug, or inhalant sensitivities. The main findings were: 1) FSR indicated sensitivities not only to foods, but also to environmental chemicals, drugs, and natural inhalants, as well as significantly more symptoms than C in multiple systems; 2) more FSR than C noted recent state depression and anxiety, as well as higher trait anxiety on the Bendig form of the Taylor Manifest Anxiety Scale; 3) however, on multiple regression analysis, not only depression, but also the number of sensitivities (foods, chemicals, drugs, inhalants), accounted for part of the variance in total number of symptoms (38 and 17%, respectively), whereas none of the affective measures accounted for any of the variance in total number of sensitivities over all subjects; 4) after controlling for depression and anxiety, FSR still showed a trend toward poorer performance on a timed mental arithmetic task (p = 0.16); and 5) FSR and C showed opposite patterns of heart rate change to two different stressful tasks (mental arithmetic and isometric exercise) (group by task interaction, p < 0.05). The data are discussed in terms of a time-dependent sensitization (TDS) process that predicts a cross-sensitizing and cross-reactive role for xenobiotic agents (e.g., foods, chemicals, drugs, and inhalants) and for salient psychological stress in the expression of psychophysiological dysfunctions of FSR. As in other chronically ill populations, negative affect in food-sensitive individuals may explain greater symptom reporting, but not necessarily account for the illness itself. For either a food or a psychological stimulus to begin to elicit sensitized responses, e.g., marked physiological differences from C, FSR may require multiple, intermittent exposures spaced over 5-28 days rather than on only 1 day.

Insulin resistance in aging is related to abdominal obesity

Studies have shown that insulin resistance increases with age, independent of changes in total adiposity. However, there is growing evidence that the development of insulin resistance may be more closely related to abdominal adiposity. To evaluate the independent effects of aging and regional and total adiposity on insulin resistance, we performed hyperinsulinemic euglycemic clamps on 17 young (21-33 yr) and 67 older (60-72 yr) men and women. We assessed FFM and total and regional adiposity by hydrodensitometry and anthropometry. Insulin-stimulated GDRs at a plasma insulin concentration of approximately 450 pM averaged 45.6 +/- 3.3 mumol.kg FFM-1 x min-1 (mean +/- SE) in the young subjects, 45.6 +/- 10.0 mumol.kg FFM-1 x min-1 in 24 older subjects who were insulin sensitive, and 23.9 +/- 11.7 mumol.kg FFM-1 x min-1 in 43 older subjects who were insulin resistant. Few significant differences were apparent in skin-fold and circumference measurements between young and insulin-sensitive older subjects, but measurements at most central body sites were significantly larger in the insulin-resistant older subjects. Waist girth accounted for > 40% of the variance in insulin action, whereas age explained only 10-20% of the total variance and < 2% of the variance when the effects of waist circumference were statistically controlled. These results suggest that insulin resistance is more closely associated with abdominal adiposity than with age.

Effects of acclimation to hypertonic environment on plasma and pituitary levels of two prolactins and growth hormone in two species of tilapia, Oreochromis mossambicus and Oreochromis niloticus

Specific radioimmunoassays (RIAs) for the pair of tilapia prolactins (tPRLs) and growth hormone (tGH) were developed using antisera raised in rabbits. Anti-tPRL177 did not cross-react with tPRL188 and tGH. Anti-tPRL188 did not cross-react with tPRL177 and showed slight cross-reaction (3.1%) with tGH. Anti-tGH showed negligible cross-reactions with tPRL177 (0.4%) and tPRL188 (1.6%). Pituitary homogenates and plasma from Oreochromis niloticus exhibited displacement curves parallel to the standards in the three RIAs. Plasma from hypophysectomized O. niloticus showed no cross-reaction in any of the three RIAs. Plasma and pituitary levels of the two PRLs in O. mossambicus in freshwater did not differ significantly from each other, whereas in O. niloticus, the levels of PRL177 were significantly greater than those of PRL188 in both plasma and pituitary. After acclimation for 3-4 weeks in seawater (O. mossambicus) or 50% seawater (O. niloticus), the levels of both PRLs decreased significantly compared to their levels in freshwater. Acclimation to a hypertonic environment did not affect plasma and pituitary GH levels in either species. Immunocytochemical staining of the pituitary of O. niloticus revealed colocalization of both PRLs in rostral pars distalis. Our findings suggest that the synthesis and secretion of the two tPRLs could be independently regulated in the same cells.

Immunocytochemical and immunogold localization of two prolactin isoforms in the same pituitary cells and in the same granules in the tilapia (Oreochromis mossambicus)

The tilapia pituitary secretes two forms of prolactin (tPRL) and a single growth hormone (tGH). The tPRLs share only 69% sequence identity and are designated tPRL177 and tPRL188 to indicate the number of amino acid residues in each isoform. Our aim was to develop specific antisera for detection of these three related polypeptides. Ten peptides corresponding to unique epitopes on the tPRLs and two peptides of tGH were synthesized using solid-phase methods, conjugated to carrier proteins, and used as immunogens for antibody production in rabbits. Select antisera for the tPRLs were highly specific, exhibiting only 1% cross-reactivity to the alternate tPRL under noncompetitive ELISA conditions at dilutions used in immunocytochemical analysis. The anti-tGH specifically bound to cells in the proximal pars distalis. Production of both tPRLs by a single cell type was indicated by the binding of both anti-tPRL177 and anti-tPRL188 to the same cells in the rostral pars distalis. Ultrastructural analysis of PRL-producing cells stained sequentially using the two different anti-tPRL antibodies labeled with immunogold of two size classes indicated that both tPRLs appear in the same granules. These findings suggest that the biological significance of two forms of PRL in the adult tilapia is not a function of differential regulation of two different classes of PRL cells or differential release of unique secretory granules.

The effect of protein supplementation on lactate accumulation during submaximal and maximal exercise

Eleven subjects performed a graded exercise test after 1 week of protein supplementation (PRO) or glucose polymer placebo (CON), randomly assigned in a double blind fashion. The exercise consisted of 3-min graded exercise bouts separated by 10 min of active recovery at zero pedal resistance. Subjects then performed a 30-sec Wingate test (WIN) to assess performance during supramaximal exercise. Blood samples were obtained in the last 15 sec of each exercise and recovery period. PRO resulted in a decrease in blood lactate following 120% VO2max and WIN, an increase in blood alanine at all time points, and lower postexercise muscle lactate and glycogen. Resting muscle GPT activity was 47% higher during the PRO trial. Mean power output during the WIN did not differ between PRO and CON. The WIN fatigue index was not significantly different between PRO and CON. The increased alanine may reflect increased transamination of pyruvate, thereby reducing the accumulation of lactate, which in turn had a marginal effect on performance during supramaximal exercise.

Multiple domains of the RNA polymerase I activator hUBF interact with the TATA-binding protein complex hSL1 to mediate transcription

Recent evidence suggests that transcription initiation by all three eukaryotic RNA polymerases involves a complex of the TATA-binding protein (TBP) and multiple TBP-associated factors (TAFs). Here, we map the functional domains of the nucleolar HMG box protein hUBF, which binds to the human rRNA promoter and stimulates transcription by RNA polymerase I through cooperative interactions with a distinct TBP-TAF complex, hSL1. DNase I footprint analysis of mutant hUBF proteins and of a synthetic peptide of 84 amino acids reveals that HMG box 1 is necessary and sufficient for DNA sequence specificity, whereas other HMG boxes and the amino terminus modulate the binding efficiency. hUBF contains multiple activation domains that include the acidic carboxyl terminus and three HMG boxes. HMG boxes 3 and 4 and the acidic tail contribute significantly to an extended footprinting pattern in the presence of hSL1, suggestive of specific protein-protein interactions. Moreover, the inability of xUBF from Xenopus laevis to form an initiation complex with hSL1 can be overcome by hybrid proteins containing human HMG box 4 and the acidic carboxyl terminus. These results strongly suggest an important role of transcription activation domains of hUBF in mediating interactions with the TBP-TAF complex hSL1.

Endoproteolytic processing of a farnesylated peptide in vitro

Numerous eukaryotic proteins containing a carboxyl-terminal CAAX motif (C, cysteine; A, aliphatic amino acid; X, any amino acid) require a three-step posttranslational processing for localization and function. The a mating factor of Saccharomyces cerevisiae is one such protein, requiring cysteine farnesylation, proteolysis of the terminal three amino acids, and carboxyl methylation for biological activity. We have used farnesylated a-factor peptides to examine the proteolytic step in the maturation of CAAX-containing proteins. Three distinct carboxyl-terminal protease activities were found in yeast cell extracts that could remove the terminal three residues of a-factor. Two of the proteolytic activities were in cytosolic fractions. One of these activities was a PEP4-dependent carboxypeptidase that was sensitive to phenylmethylsulfonyl fluoride. The other cytosolic activity was PEP4-independent, sensitive to 1,10-phenanthroline, and effectively inhibited by an unfarnesylated a-factor peptide. In contrast, a protease activity in membrane fractions was unaffected by phenylmethylsulfonyl fluoride, 1,10-phenanthroline, or unfarnesylated a-factor peptide. Incubation of membrane preparations from either yeast or rat liver with a radiolabeled farnesylated a-factor peptide released the terminal three amino acids intact as a tripeptide, indicating that this reaction occurred by an endoproteolytic mechanism and that the enzyme most likely possesses a broad substrate specificity. The yeast endoprotease was not significantly affected by a panel of protease inhibitors, suggesting that the enzyme is novel. Zinc ion was shown to inhibit the endoprotease (Ki less than 100 microM). The specific activities of the a-factor carboxyl-terminal membrane endoprotease and methyltransferase clearly indicated that the proteolytic reaction was not rate-limiting in these processing reactions in vitro.

Skeletal muscle adaptations to endurance training in 60- to 70-yr-old men and women

Previous studies of endurance exercise training in older men and women generally have found only minimal skeletal muscle adaptations to training. To evaluate the possibility that this may have been due to an inadequate training stimulus, we studied 23 healthy older (64 +/- 3 yr) men and women before and after they had trained by walking/jogging at 80% of maximal heart rate for 45 min/day 4 days/wk for 9-12 mo. This training program resulted in a 23% increase in maximal O2 consumption. Needle biopsy samples of the lateral gastrocnemius muscle were obtained before and after training and analyzed for selected histochemical and enzymatic characteristics. The percentage of type I muscle fibers did not change with training. The percentage of type IIb fibers, however, decreased from 19.1 +/- 9.1 to 15.1 +/- 8.1% (P less than 0.001), whereas the percentage of type IIa fibers increased from 22.1 +/- 7.7 to 29.6 +/- 9.1% (P less than 0.05). Training also induced increases in the cross-sectional area of both type I (12%; P less than 0.001) and type IIa fibers (10%; P less than 0.05). Capillary density increased from 257 +/- 43 capillaries/mm2 before training to 310 +/- 48 capillaries/mm2 after training (P less than 0.001) because of increases in the capillary-to-fiber ratio and in the number of capillaries in contact with each fiber. Lactate dehydrogenase activity decreased by 21% (P less than 0.001), whereas the activities of the mitochondrial enzymes succinate dehydrogenase, citrate synthase, and beta-hydroxyacyl-CoA dehydrogenase increased by 24-55% in response to training (P less than 0.001-0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Histochemical and enzymatic comparison of the gastrocnemius muscle of young and elderly men and women

To examine the effects of aging on human skeletal muscle, 10 men and 10 women, 64 +/- 1 yr old (Mean +/- SE), and 10 men and 10 women, 24 +/- 1 yr old, were studied. All subjects were sedentary nonsmokers who were carefully screened for latent cardiovascular, metabolic, or musculoskeletal disease. Needle biopsy samples were obtained from the lateral gastrocnemius muscle and examined using histochemical and biochemical techniques. The percentage of Type I, Type IIa, and Type IIb fibers did not differ with age. However, Type I fibers occupied a larger percent of total muscle area in the older men and women (60.6 +/- 2.6 vs 53.6 +/- 2.0%; p less than .05), because Type IIa and Type IIb fibers were 13-31% smaller (p less than .001) in these subjects. Muscle capillarization and mitochondrial enzyme (i.e., succinate dehydrogenase, citrate synthase, and beta-hydroxyacyl-CoA dehydrogenase) activities were also approximately 25% lower (p less than .001-.05) in the old subjects. Although it is difficult to determine whether these differences are due to aging itself or are simply due to inactivity, these structural and biochemical changes probably contribute to the decreases in muscle mass, strength, and endurance often observed in healthy but sedentary older men and women.

Identification of the glucocorticoid suppressible mitogen from rat hepatoma cells as an angiogenic platelet-derived growth factor A-chain homodimer

We have previously shown that BDS.1 rat hepatoma cells are hypersensitive to the antiproliferative effects of glucocorticoids, and secrete a glucocorticoid suppressible mitogenic activity (denoted GSM). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that GSM purified to near homogeneity migrated as a 28-kDa protein under nonreducing conditions and as a single 15-kDa polypeptide in the presence of sulfhydryl reducing agents suggesting a homodimeric structure. Anti-platelet-derived growth factor (PDGF) A-chain specific antibodies selectively immunodepleted the mitogenic activity which can be extracted from nonreducing gels in the 26-30-kDa fraction and, in Western blots, recognized the 15-kDa reduced form of GSM. Western blot analysis further showed that dexamethasone suppressed the level of secreted PDGF A-chain protein in BDS.1 cells but not in glucocorticoid receptor-deficient hepatoma cells. Northern blots revealed that dexamethasone reduced expression of the PDGF A-chain 2.3- and 1.7-kilobase transcripts in proportion to the level of detectable PDGF-AA protein. Similarly to PDGF-AA, the hepatoma cell-derived GSM has a potent angiogenic activity. Taken together, our results demonstrate that the predominant glucocorticoid suppressible mitogen secreted from rat hepatoma cells is a PDGF A-chain homodimer and suggest that in vivo glucocorticoids may potentially regulate hepatoma growth by modulating PDGF-stimulated tumor vascularization.

Identification of a diuretic hormone of Locusta migratoria

We have isolated a peptide from brains and corpora cardiaca of Locusta migratoria which is immunologically related to the diuretic hormone of Manduca sexta. We determined its structure as a 46 amino acid linear peptide with 43-50% identity to the M. sexta hormone. Moreover, we showed that the new peptide functions as a diuretic hormone in L. migratoria, stimulating urine production by Malpighian tubules and elevating levels of cAMP in tubules.

Amino acid sequence of growth hormone isolated from medium of incubated pituitary glands of tilapia (Oreochromis mossambicus)

The amino acid sequence of tilapia (Oreochromis mossambicus) growth hormone (GH) was determined directly by Edman degradation of peptide fragments generated by lysyl endopeptidase and trypsin digestion. The N-terminal residue was deduced to be pyroglutamic acid through the use of pyroglutamyl aminopeptidase; its removal allowed amino acid sequence determination of the remainder of the N-terminal trypsin peptide by Edman degradation. Tilapia GH is composed of 187 amino acid residues and shows high similarity to other perciform GHs. Sequence identities are: 89% with tuna GH, 83% with bonito GH, 85% with yellowtail GH, 89% with red sea bream GH, and 34% with bovine GH. The two asparagine residues (Asn-148 and Asn-184) were recovered by Edman degradation, suggesting the absence of N-glycosylation.

Depression and allergies: survey of a nonclinical population

The possible association between depression and type I allergies (i.e. immunoglobulin E-mediated hay fever, asthma, eczema, hives) was examined in a nonclinical sample of 379 college students. Measures included self-reports of depression, tiredness, fearfulness, allergic disorders, and environmental allergens and irritants. Seventy-one percent of the subjects who had ever received a professional diagnosis of depression also indicated a history of allergy: those with greater self-rated current depression overall reported a significantly higher prevalence of asthma (p less than 0.05). Type I allergic (43%) and nonallergic subjects did not differ in self-rated frequency of depression, fatigue, or anxiety. However, type I subjects reported significantly worse mood after the flu than did nonallergic subjects (p less than 0.001). The data support the hypothesis that individuals prone to clinical depression have more allergies than nondepressives. Allergics may experience more postflu mood worsening but not current depression in comparison with nonallergics.

Interactions of PRP2 protein with pre-mRNA splicing complexes in Saccharomyces cerevisiae

PRP2 protein of Saccharomyces cerevisiae is required for the pre-mRNA splicing reaction but not for the early stages of spliceosome assembly. Using anti-PRP2 antibodies we demonstrate that PRP2 protein is associated with spliceosomes prior to, and throughout step 1 of the splicing reaction. Heat-inactivated prp2 protein, by contrast, does not seem to associate with spliceosomes. By elution of electrophoretically distinct spliceosomal complexes from non-denaturing gels we identify the specific complex with which PRP2 initially interacts in the pathway of spliceosome assembly.

Effect of exercise on glucose disposal: response to a maximal insulin stimulus

We used the euglycemic clamp to assess the effects of exercise on maximally insulin-stimulated glucose disposal. In 11 young men, a 60-min bout of exercise had no significant effect on the rate of glucose disposal during a euglycemic clamp performed approximately 30 min postexercise in which plasma insulin was raised to approximately 2,500 microU/ml (a maximal insulin stimulus). The maximal rate of glucose disposal attained during the clamp averaged 15.7 +/- 1.0 mg.kg lean body mass-1.min-1 after exercise vs. a control value of 15.4 mg.kg lean body mass-1.min-1. In a second experiment, eight men performed supine cycle exercise during the 3rd h of a 4-h euglycemic clamp with a plasma insulin concentration of approximately 2,500 microU/ml. Exercise during the hyperinsulinemic clamp resulted in a 70% increase in glucose disposal rate. There was no measurable increase in glucose 6-phosphate in the quadriceps muscle during the insulin infusion at rest. We conclude that prior exercise does not enhance maximally insulin-stimulated glucose disposal in young healthy men. Our results are compatible with the interpretations that glucose availability rather than glucose metabolism limits the rate of glucose disposal in response to a maximal insulin stimulus in resting subjects and that the increase in glucose uptake in response to superimposed exercise is primarily due to an increase in glucose availability.

A cleavage method which minimizes side reactions following Fmoc solid phase peptide synthesis

The success of solid phase peptide synthesis utilizing 9-fluorenylmethoxycarbonyl (Fmoc) amino acids is often limited by deleterious side reactions which occur during TFA peptide-resin cleavage and side-chain deprotection. The majority of these side reactions modify susceptible residues, such as Trp, Tyr, Met, and Cys, with TFA-liberated side-chain protecting groups and linkers. The purpose of this study was to assess the relative effectiveness of various scavengers in suppressing these side reactions. We found that the cleavage mixture 82.5% TFA : 5% phenol : 5% H2O : 5% thioanisole : 2.5% EDT (Reagent K) was maximally efficient in inhibiting a great variety of side reactions. Synthesis and cleavage of 10 peptides, each containing 20-50 residues, demonstrated the complementarity of Fmoc chemistry with Reagent K for efficient synthesis of complex peptides.

Ecdysone-dependent proteolysis of an apical surface glycoprotein may play a role in imaginal disc morphogenesis in Drosophila

An apical surface glycoprotein, designated gp125 for its apparent molecular weight of 125,000, appears in Ca2(+)-free, ionic detergent extracts of imaginal discs of Drosophila melanogaster in response to the steroid hormone, 20-hydroxyecdysone (20-HE). Gp125 is not synthesized in response to 20-HE, but results from modification of an existing macromolecule. Treatment of discs or larval epidermis with serine protease (e.g., trypsin) results in hormone-independent production of gp125. Antiserum raised to electrophoretically purified gp125 recognizes, in addition to gp125, two closely related glycoproteins with higher apparent molecular weights, gp200 and gp180. This family of glycoproteins is localized at the apical surface of imaginal disc cells and of the epidermal epithelium in embryos, larvae and prepupae. Ca2+ affects both the solubility and the proteolytic products of this family of glycoproteins. We discuss the possibility that gp125 is generated through the action of a hormonally controlled serine protease in a process that is necessary for disc morphogenesis.

Is allergic rhinitis more frequent in young adults with extreme shyness? A preliminary survey

Previous studies suggest that social anxiety, allergies and distressed affect may be interrelated in some persons. For example, extremely introverted patients experience a poorer course and outcome of allergies as well as greater degrees of distressed affect such as depression and anxiety than do extraverts. Patients with affective disorders have a higher prevalence of atopic allergy than the general population; families of patients with panic disorder and major depression have the highest frequency of shy children. Preliminary investigation also indicate that behaviorally inhibited Caucasian children (initially shy and cautions in unfamiliar situations) and their families have more allergies, especially hay fever, than do uninhibited, socially outgoing children. The present survey evaluated the frequency of self-reported shyness. The most introverted subjects had significantly higher scores on self reports of depression, fearfulness, and fatigue, as well as a higher prevalence of hay fever. The data support the possibility of a distinct subgroup of shy individuals with concomitant vulnerability to specific allergies and affective disorders.

Insulin secretory capacity in endurance-trained and untrained young men

Insulin secretion in response to glucose stimulation is reduced in endurance-trained humans. In this study, a modified hyperglycemic clamp, with a superimposed arginine infusion and fat meal, was performed on eight endurance-trained and nine untrained men to determine whether insulin secretory capacity is reduced by exercise training. Raising the plasma glucose concentration to approximately 450 mg/dl resulted in a plasma insulin response in the trained men that was approximately 64% lower than that of the untrained (peak values: 54 +/- 8 vs. 149 +/- 35 microU/ml; P less than 0.001). When a primed continuous infusion of arginine was superimposed on the hyperglycemia, the plasma insulin response was also markedly lower (66%) in the trained subjects, reaching peak values of 333 +/- 68 and 974 +/- 188 microU/ml for trained and untrained subjects, respectively (P less than 0.005). When insulin secretion was further stimulated during the arginine-infused hyperglycemia by the ingestion of a high-fat meal, peak insulin concentrations averaged 989 +/- 205 microU/ml in the trained compared with 2,232 +/- 455 microU/ml in the untrained subjects (P less than 0.01). The response of gastric inhibitory polypeptide (GIP) to the fat meal was delayed and blunted, suggesting that some enteric factor(s) other than GIP mediated the insulinotropic effect of the fat meal. The reduced plasma insulin response in trained people to the stimuli investigated suggests that regular exercise produces either several adaptations within the beta-cell or a single alteration of the beta-cell that results in an attenuation of the insulin secretory response to glucose, arginine, and fat ingestion.

Type II fiber activation with electrical stimulation: a preliminary report

Electrical stimulation to augment or maintain muscle performance has been well documented. The purpose of this preliminary report is to present the results of a single-case study conducted to determine the order of activation of skeletal muscle fibers as a result of electrical stimulation. The subject's quadriceps femoris muscles were electrically stimulated at 80% of maximal isometric torque. Pre-stimulation and immediate post-stimulation muscle biopsy samples were obtained, and a modification of the glucogen-depletion method was used to determine activation of muscle fibers. The pre-stimulation muscle biopsy sample demonstrated uniform periodic acid-Schiff (PAS)-positive staining in all fiber types, whereas the post-stimulation muscle biopsy sample showed glycogen depletion of type II muscle fibers. The most PAS-negative muscle fibers were type IIa skeletal muscle fibers. The results of this single-case study provide evidence that electrical stimulation, as described, selectively activates type II skeletal muscle fibers. The implication of this finding is that, in many chronic diseases, type II fibers are selectively and preferentially affected. Electrical stimulation may be a clinically viable technique to use in patients with type II fiber involvement.

Effect of 10 days of physical inactivity on glucose tolerance in master athletes

Master athletes who exercise regularly appear to avoid the development of insulin resistance and deterioration of glucose tolerance (GT) commonly seen with aging. To evaluate the possibility that exercise prevents rather than masks the aging-related changes responsible for development of insulin resistance, we investigated the effects of 10 days of physical inactivity in 14 master athletes aged 61 +/- 2 (SE) yr. The response of 10 of these men to inactivity was similar to that of young athletes, with an unchanged plasma glucose response and a significantly greater insulin response to an oral glucose tolerance test (OGTT) after 10 days of inactivity. These 10 athletes appeared to have been protected against the aging-related changes in GT because their plasma glucose and insulin levels during the OGTT after 10 days of inactivity were not significantly different from those of young lean sedentary men. In contrast, a deterioration in GT occurred in four of the master athletes during 10 days of inactivity; this was sufficiently marked in two of them to be classified as impaired GT. We conclude that regular exercise may 1) protect against the development of insulin resistance and decline in GT with aging in individuals with normal GT and 2) normalize GT by means of short-term effects of exercise in some individuals with abnormal GT.

Histochemical and enzymatic characteristics of skeletal muscle in master athletes

Many older athletes are capable of endurance performances equal to those of young runners who have higher maximal O2 uptakes (VO2max). To determine whether this is a result of differences in skeletal muscle characteristics, gastrocnemius muscle biopsy samples were obtained from eight master athletes [aged 63 +/- 6 (SD) yr] and eight young (aged 26 +/- 3 yr) runners. The young runners were matched with the master athletes for 10-km running performance and for their volume, pace, and type of training. Despite similar 10-km run times, VO2max was 11% lower (P less than 0.05) in the master athletes. Fiber type distribution did not differ between groups, with both groups having 60% type I and very few type IIb fibers. Succinate dehydrogenase and beta-hydroxyacyl-CoA dehydrogenase activities, however, were 31 and 24% higher in the master athletes compared with the matched young runners, whereas lactate dehydrogenase activity was 46% lower (all P less than 0.05). The capillary-to-fiber ratio was also greater in the master athletes; however, capillary density was similar in the two groups, because of the master athletes' 34% larger (P less than 0.05) type I fibers. These differences in skeletal muscle characteristics may explain the master athletes' ability to perform as well as some young runners despite having a lower VO2max.

Exercise and recovery ventilatory and VO2 responses of patients with McArdle's disease

This study was designed to determine whether patients with McArdle's disease, who do not increase their blood lactate levels during and after maximal exercise, have a slow "lactacid" component to their recovery O2 consumption (VO2) response after high-intensity exercise. VO2 was measured breath by breath during 6 min of rest before exercise, a progressive maximal cycle ergometer test, and 15 min of recovery in five McArdle's patients, six age-matched control subjects, and six maximal O2 consumption- (VO2 max) matched control subjects. The McArdle's patients' ventilatory threshold occurred at the same relative exercise intensity [71 +/- 7% (SD) VO2max] as in the control groups (60 +/- 13 and 70 +/- 10% VO2max) despite no increase and a 20% decrease in the McArdle's patients' arterialized blood lactate and H+ levels, respectively. The recovery VO2 responses of all three groups were better fit by a two-, than a one-, component exponential model, and the parameters of the slow component of the recovery VO2 response were the same in the three groups. The presence of the same slow component of the recovery VO2 response in the McArdle's patients and the control subjects, despite the lack of an increase in blood lactate or H+ levels during maximal exercise and recovery in the patients, provides evidence that this portion of the recovery VO2 response is not the result of a lactacid mechanism. In addition, it appears that the hyperventilation that accompanies high-intensity exercise may be the result of some mechanism other than acidosis or lung CO2 flux.

Improvement in glucose tolerance after 1 wk of exercise in patients with mild NIDDM

We investigated the effects of 1 wk of intense exercise on glucose tolerance in 10 men with abnormal glucose tolerance [7 had mild non-insulin-dependent diabetes mellitus (NIDDM), and 3 had impaired glucose tolerance]. The 7 days of exercise did not result in significant changes in body weight or maximal oxygen uptake. Plasma glucose concentration at 120 min averaged 227 +/- 23 mg/dl in an oral glucose tolerance test (OGTT) before and 170 +/- 18 mg/dl after the 7 days of exercise (P less than .001). There was a 36% reduction in the area under the glucose tolerance curve. Plasma insulin concentration at 120 min of the OGTT averaged 172 +/- 27 microU/ml before and 106 +/- 13 microU/ml after 7 days of exercise (P less than .001); the area under the insulin curve was decreased by 32%. In contrast to the response to 7 days of exercise, one bout of exercise did not result in an improvement in glucose tolerance. These results provide evidence that regularly performed, vigorous exercise can be effective in decreasing insulin resistance and improving glucose tolerance within 7 days in some patients with mild NIDDM.

Complete amino acid sequences of a pair of fish (tilapia) prolactins, tPRL177 and tPRL188

The complete amino acid sequences of a pair of tilapia (Oreochromis mossambicus) prolactins (PRLs) were determined. The larger PRL of molecular mass 20,836 Da consists of 188 amino acid residues. The smaller PRL of molecular mass 19,584 Da is 11 residues shorter. On alignment of the two sequences, the 19.6-kDa PRL (tPRL177) has two conspicuous deletions on the NH2-terminal side of the disulfide bond which connects the first and second cysteine residues. The degree of similarity between the two PRL sequences is unexpectedly low (130 identical residues, 69%) compared with that between the variants of other teleostean PRLs. Circular dichroism spectra and hydropathy profiles suggest structural similarity of the two PRLs. The sequence of the 20.8-kDa PRL (tPRL188) has 69% identity with that of salmon PRL. The sequence of tPRL177 is 56% identical with that of salmon PRL. Each tilapia PRL is equally similar to mammalian PRLs (about 30% identical residues). Regions highly conserved among teleostean and mammalian PRLs were identified on the COOH-terminal side of the disulfide bond connecting the first and second cysteine residues.

Effects of lack of exercise on insulin secretion and action in trained subjects

We employed the hyperglycemic clamp technique to investigate the effects of short-term inactivity on insulin secretion in nine (8 men, 1 woman) well-trained subjects. A 3-h hyperglycemic clamp (plasma glucose approximately 180 mg/100 ml) was performed approximately 16 h after a usual training bout and again 14 days after stopping exercise training. There was no significant change in body composition during this short period of inactivity. The mean plasma insulin response to an identical glycemic stimulus was 67% higher after 14 days without exercise (45 +/- 7 after vs. 27 +/- 4 microU/ml before stopping exercise training). Marked increases in the early (0-10 min, 150 +/- 28 vs. 101 +/- 15 microU.ml-1.min) and late (10-180 min, 6,051 +/- 1,257 vs. 3,521 +/- 749 microU.ml-1.min) incremental insulin areas were observed as a result of the physical inactivity. Incremental areas for C-peptide were also elevated significantly in the inactive state for early (12 +/- 2.0 vs. 7 +/- 1 ng.ml-1.min) and late (567 +/- 90 vs. 467 +/- 85 ng.ml-1.min) phases. Urinary excretion of C-peptide increased from 12.1 +/- 1.5 ng/240 min in the exercising state to 21.8 +/- 3.6 ng/240 min in the inactive state. Rates of whole body glucose disposal were not different between exercising and inactive states, indicating a large increase in resistance to the action of insulin. These findings indicate that the decreased insulin secretory response to a glucose stimulus in people who exercise regularly is a relatively short-term effect of exercise.

Effects of exercise and lack of exercise on insulin sensitivity and responsiveness

Insulin action is enhanced in people who exercise regularly and vigorously. In the present study, the hyperinsulinemic, euglycemic clamp procedure was used to determine whether this enhanced insulin action is due to an increased sensitivity and/or an increased responsiveness to insulin. To avoid the variability that exists between individuals and complicates cross-sectional studies, the same subjects were studied in the trained exercising state and again after 10 days of physical inactivity. When the plasma insulin concentration was maintained at approximately 78 microU.ml-1 (a submaximal level), glucose disposal rate averaged 8.7 +/- 0.5 mg.kg-1.min-1 before and 6.7 +/- 0.6 mg.kg-1.min-1 after 10 days of activity (P less than 0.001). When the plasma insulin concentration was maintained at approximately 2,000 microU.ml-1 (a maximally effective concentration), the rate of glucose disposal was not significantly different before (15.3 +/- 0.5 mg.kg-1.min-1) compared with after (14.5 +/- 0.4 mg.kg-1.min-1) 10 days without exercise. These results provide evidence that the reversal of enhanced insulin action that occurs within a few days when exercise-trained individuals stop exercising is due to a decrease in sensitivity to insulin, not to a decrease in insulin responsiveness.

A novel method for measurement of triglyceride lipase activity: suitable for microgram and nanogram quantities of tissue

The measurement of triglyceride lipase activity in microgram and nanogram quantities of tissue is reported. The method involves quantitation of glycerol released from a triglyceride substrate, which is shown to provide a value of approximately one-third of that obtained by quantitation of free fatty acid release. Influences on glycerol release, including pH optimum, NaCl inhibition, and activation by serum and heparin are characterized. Two separate assays are described for the measurement of glycerol that yield identical results with nanogram quantities of tissue. The advantage of one assay is its simplicity, while the advantage of the other is that it can be adjusted to measure very small tissue samples (nanogram) with the use of microanalytical procedures (i.e., enzymatic amplification of the NAD+ product of glycerol analysis). Sensitivity of the method is demonstrated by the analysis of triglyceride lipase activity in nanogram samples of single soleus muscle fibers. Measurement of picomole quantities of glycerol produced by lipase activity in single muscle fibers represents at least a 1,000-fold increase in sensitivity compared to currently available methods.

The reliability and validity of provocative food testing: a critical review

Clinical reports have advocated intradermal and sublingual provocative food testing as effective methods of identifying food sensitivities. However, studies assessing their reliability and/or validity have generally reached negative conclusions. These studies commonly have serious flaws in design and analysis. These include: (1) the administration of food antigens to subjects without verifying sensitivity to them, and then comparing responses to antigens and placebos, (2) the failure to implement double-blind procedures with placebo controls, (3) the failure to analyse results statistically, and (4) improper statistical analysis. In some cases, re-analysis of the data provided seriously affects the conclusions of the study. Overall, the evidence suggests that both intradermal and sublingual provocative food tests are capable of provoking reactions above placebo levels, but whether they are sufficiently reliable and valid to be clinically useful is questionable.

The primary structure of coho salmon growth hormone and its cDNA

Total RNA was extracted from coho salmon growth hormone (sGH) cell regions and used to synthesize double-stranded cDNA, which was inserted into a plasmid vector and used to transform Escherichia coli HB101. The total RNA was also separated according to size by electrophoresis on agarose gels and the fraction that directed the cell-free synthesis of protein in the size range of GHs of other species was isolated and used to screen the transformed colonies of E. coli. A clone containing the putative sGH cDNA was identified and its nucleotide sequence was determined. To verify that the cDNA was that of sGH, the GH cell region of coho pituitary glands was incubated in organ culture. The secreted GH was purified by HPLC and the sequence of its 42 amino-terminal amino acids was determined. Comparison of this sequence with the amino acid sequence derived from the cDNA showed that it encoded sGH. Medium containing the presumptive sGH as the only prominent protein was active in a GH radioreceptor assay that involved labeled bovine GH and pregnant mouse liver membranes: the sGH was approximately 10% as active as the bGH standard. RNA blotting analysis showed that sGH was the major species of RNA produced by the GH cell region of the salmon pituitary. The mRNA of sGH differed from those of human, rat, and bovine GH in that its 3'-untranslated region was unusually large (about 500 nucleotides) but the coding region showed significant homology with mammalian GHs and resembled them in having a strong (78%) preference for G and C in the third positions of the codons. The amino acid sequence of sGH showed 32-34% and 19-22% identical homology with mammalian GHs and prolactins, respectively. Several conserved regions between sGH and mammalian GH and PRL molecules were also revealed that could indicate conservation of structurally and/or functionally important domains. Hydropathy analysis disclosed that although sGH and the GH of a representative mammal (pig) had similar profiles in some regions, the sGH was overall more hydrophobic than the pig (p) GH. Similarities and differences, were also noted in the predicted secondary structure of sGH and pGH.

Insulin action and secretion in endurance-trained and untrained humans

To evaluate insulin sensitivity and responsiveness, a two-stage hyperinsulinemic euglycemic clamp procedure (insulin infusions of 40 and 400 mU.m-2.min-1) was performed on 11 endurance-trained and 11 untrained volunteers. A 3-h hyperglycemic clamp procedure (plasma glucose approximately 180 mg/dl) was used to study the insulin response to a fixed glycemic stimulus in 15 trained and 12 untrained subjects. During the 40-mU.m-2.min-1 insulin infusion, the glucose disposal rate was 10.2 +/- 0.5 mg.kg fat-free mass (FFM)-1.min-1 in the trained group compared with 8.0 +/- 0.6 mg.kg FFM-1.min-1 in the untrained group (P less than 0.01). In contrast, there was no significant difference in maximally stimulated glucose disposal: 17.7 +/- 0.6 in the trained vs. 16.7 +/- 0.7 mg.kg FFM-1.min-1 in the untrained group. During the hyperglycemic clamp procedure, the incremental area for plasma insulin was lower in the trained subjects for both early (0-10 min: 140 +/- 18 vs. 223 +/- 23 microU.ml-1.min; P less than 0.005) and late (10-180 min: 4,582 +/- 689 vs. 8,895 +/- 1,316 microU.ml-1.min; P less than 0.005) insulin secretory phases. These data demonstrate that 1) the improved insulin action in healthy trained subjects is due to increased sensitivity to insulin, with no change in responsiveness to insulin, and 2) trained subjects have a smaller plasma insulin response to an identical glucose stimulus than untrained individuals.

Polarized secretion of an ectopic protein in Drosophila salivary glands in vivo

Epithelial cells can secrete specific proteins in a polarized manner, either from the apical or basolateral surface. Intracellular protein sorting which results in polarized secretion has previously been studied using epithelial tissue culture cells. We describe here the use of Drosophila larval salivary glands for the study of polarized secretion by epithelia in vivo, and address whether an ectopically synthesized secretory protein can be sorted and targeted to the correct cell surface for secretion. Larval cuticle proteins (LCPs) and salivary gland secretion (Sgs) proteins of Drosophila melanogaster are apically secreted proteins that are produced respectively by the epidermis and salivary glands. We have transformed Drosophila with a hybrid gene consisting of the sgs-4 promoter sequence and the coding sequence for a variant (LCP-f2) of LCP-2. We have found that transgenic late third instar larvae produce LCP-f2 only in the salivary glands and that LCP-f2 is properly secreted in vivo in a polarized manner from only the apical surface of the cells into the gland lumen. The results indicate that apical secretion does not depend on a tissue-specific targeting signal contained within the protein.

Effect of pre-exercise carbohydrate feedings on endurance cycling performance

Six men were studied to compare the effects of pre-exercise carbohydrate feedings on endurance performance and muscle glycogen utilization during prolonged exercise. Trials consisted of a cycling ride to exhaustion at 75% maximal oxygen uptake preceded by the ingestion of either 75 g of glucose in 350 ml of water (GLU), 75 g of fructose in 350 ml of water (FRU), or 350 ml of an artificially sweetened and flavored placebo (CON). No differences were observed between trials for oxygen uptake, respiratory exchange ratio, heart rate, or exercise time to exhaustion (CON = 92.7 +/- 5.2 min, FRU = 90.6 +/- 12.4, and GLU = 92.8 +/- 11.3, mean +/- SE). Blood glucose was elevated as a result of the GLU feeding, but fell rapidly with the onset of exercise, reaching a low of 4.02 +/- 0.34 mmol X l-1 at 15 min of exercise. Serum insulin also increased following the GLU feeding but had returned to pre-drink levels by 30 min of exercise. No differences in blood glucose and insulin were observed between FRU and CON. Muscle glycogen utilization during the first 30 min of exercise (CON = 46.3 +/- 8.2 mmol X kg-1 wet weight, FRU = 56.3 +/- 3.0 mmol X kg-1 wet weight, GLU = 50.0 +/- 4.9 mmol X kg-1 wet weight) and total glycogen use (CON = 93.4 +/- 11.1, FRU = 118.8 +/- 10.9, and GLU = 99.5 +/- 4.3) were similar in the three trials.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of pre-exercise carbohydrate feedings on muscle glycogen use during exercise in well-trained runners

The purpose of this study was to examine the effects of pre-exercise glucose and fructose feedings on muscle glycogen utilization during exercise in six well-trained runners (VO2max = 68.2 +/- 3.4 ml X kg-1 X min-1). On three separate occasions, the runners performed a 30 min treadmill run at 70% VO2max. Thirty minutes prior to exercise each runner ingested 75 g of glucose (trial G), 75 g of fructose (trial F) or 150 ml of a sweetened placebo (trial C). During exercise, no differences were observed between any of the trials for oxygen uptake, heart rate or perceived exertion. Serum glucose levels were elevated as a result of the glucose feeding (P less than 0.05) reaching peak levels at 30 min post-feeding (7.90 +/- 0.24 mmol X l-1). With the onset of exercise, glucose levels dropped to a low of 5.89 +/- 0.85 mmol X l-1 at 15 min of exercise in trial G. Serum glucose levels in trials F and C averaged 6.21 +/- 0.31 mmol X l-1 and 5.95 +/- 0.23 mmol X l-1 respectively, and were not significantly different (P less than 0.05). There were also no differences in serum glucose levels between any of the trials at 15 and 30 min of exercise.

The two-photon laser-induced fluorescence of the tumor-localizing photosensitizer hematoporphyrin derivative. Resonance-enhanced 750 nm two-photon excitation into the near-UV Soret band

The tumor-localizing photosensitizer hematoporphyrin derivative (HPD) is shown to undergo a simultaneous two-photon excitation into the near-ultraviolet Soret band system upon intense laser irradiation at 750 nm, a spectral region where there is no significant HPD one-photon absorbance in aqueous solution. Subsequent to this excitation, internal conversion and vibrational relaxation occur, resulting in the population of the vibrationless level of the first electronically excited singlet state. This state relaxes by two channels, the emission of fluorescence in the spectral region 600-700 nm and intersystem crossing into the triplet manifold, followed by near-resonant electronic energy transfer with surrounding oxygen to result in the generation of highly reactive singlet molecular oxygen (1 delta g). Evidence for the two-photon excitation consists in the observation both of the HPD fluorescence spectrum in the region of 615 nm as a result of 750 nm excitation and the quadratic dependence of this fluorescence emission intensity upon the excitation laser intensity. Since, in general, the penetration depth of ultraviolet and visible light into tissue varies directly with wavelength (red penetrating more deeply than blue), these studies suggest the possibility that two-photon-induced localization of tumor-bound HPD might facilitate the detection of deeper lying tumors than allowed by the current one-photon photolocalization method.