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Biomedical subjects

D Borovsky

Publications and source records attributed to D Borovsky.

35 records · Page 2Linked to original sources
PubMed1992

Biosynthesis of trypsinlike and chymotrypsinlike enzymes in immature Lutzomyia anthophora (Diptera: Psychodidae).

The biosynthesis of trypsinlike and chymotrypsinlike enzymes was followed in the four instars and pupa of Lutzomyia anthophora Addis. A 32-fold increase in the biosynthesis of trypsinlike enzymes was observed from the first to the fourth instar. Trypsinlike and chymotrypsinlike isozymes were also synthesized by pupae 1-8 d old. Similarly, a 29-fold increase in the biosynthesis of chymotrypsinlike isozymes also was observed from first to fourth instars. Several different [1,3-3H]DIP trypsinlike and chymotrypsinlike derivatives of first to fourth instars and pupae (1 and 8 d old) were studied using polyacrylamide gel electrophoresis and fluorography.

Animals↗
PubMed1992

Biosynthesis and metabolism of juvenile hormone III from methyl farnesoate by exposed corpora allata of Lutzomyia anthophora.

The in-vitro biosynthesis of [12-3H] juvenile hormone (JH) III by exposed corpora allata (CA) of teneral, sugar-fed, and blood-fed female Lutzomyia anthophora (Addis) was followed by incubating the CA for 4 h with [12-3H]methyl farnesoate. Synthesis of [12-3H]H III was determined by C18 reversed-phase high-pressure liquid chromatography (HPLC) and preparative gas chromatography. The rate of synthesis of JH III by teneral females was 5.6 fmol/h per CA. The CA of 1-d-old females synthesized 17 fmol/h per CA, whereas 3-d-old females synthesized 5.4 fmol/h per CA. The rate of synthesis of JH III 4 h after the blood meal increased to 17.3 fmol/h per CA and then declined to reach a minimum of 1.6 fmol/h per CA at 30 h before increasing again to reach 21.6 fmol/h per CA at 96 h. The concentration of methyl farnesoate in the tissue culture medium during incubation of CA from sugar- and blood-fed females was compared with the rate of synthesis of JH III and its metabolites diol-acid, diol, acid, and bisepoxide. The rate of synthesis of JH III and its metabolites from methyl farnesoate indicated a steady-state equilibrium of synthesis and metabolism of JH III by the exposed CA. The rapid increase in JH III synthesis immediately after the blood meal confirmed that in sand flies, like mosquitoes, there is an increase in the rate of synthesis of JH III immediately after the female takes blood. The role of the hormone in vitellogenin biosynthesis is also discussed.

Animals↗
PubMed1992

In vivo and in vitro biosynthesis and metabolism of methyl farnesoate, juvenile hormone III, and juvenile hormone III acid in the mosquito Aedes aegypti.

Biosynthesis and metabolism of juvenile hormone (JH) III in vivo and in vitro were studied in female Aedes aegypti (L.). [12-3H]Methyl farnesoate was used to follow the synthesis and [12-3H]-(10R)-JH III to study metabolism. The rate of biosynthesis of [12-3H]JH III in vivo after adult eclosion increased from 9 fmol/h per female at 1 h to 22 fmol/h per female at day 6. The rate of biosynthesis by exposed corpora allata (CA) in vitro was 23 fmol/h per CA during the 1st d after adult eclosion, then dropped to 4.8 fmol/h per CA on day 3, then increased again to a constant level of synthesis (12 fmol/h per CA) at days 4-6. Immediately after blood feeding, the rate of synthesis of [12-3H]JH III in vivo and in vitro increased to 27 fmol/h per female and to 23 fmol/h per CA, respectively. The rate of synthesis then decreased in vivo to 12 fmol/h per female at 4 h and in vitro to 6 fmol/h per CA 10 h after the blood meal. After this decrease, the rate of synthesis of [12-3H]JH III increased again reaching a peak of 25 fmol/h per female at 48-96 h in vivo and 12 fmol/h per CA at 72 h in vitro. These results indicated that the CA of sugar-fed and blood-fed female A. aegypti synthesized JH III in vivo and in vitro from [12-3H]methyl farnesoate. When [12-3H]-(10R)-JH III metabolism was followed in vivo in female A. aegypti, the ratio between JH III diol acid:JH III acid:JH III diol was 17:4:1, indicating that JH III was first hydrolyzed by JH III esterase to the acid form, then hydrated to the diol acid by JH III epoxide hydrase. Females treated with [12-3H]JH III acid converted 46% of the JH III acid in 60 min to the diol acid. These results indicated that the enzyme epoxide hydrase acted on JH III acid 17 times faster than JH III.

Aedes↗
PubMed1990

Mosquito oostatic factor: a novel decapeptide modulating trypsin-like enzyme biosynthesis in the midgut.

A peptide that inhibits egg development in mosquitoes (oostatic factor) has been purified from the ovaries of female Aedes aegypti. The factor is a decapeptide with a molecular mass of 1047.6. The primary sequence has been determined as NH2-Tyr-Asp-Pro-Ala-Pro-Pro-Pro-Pro-Pro-Pro-COOH from mass spectra recorded on a quadrupole Fourier transform instrument. The amino acid sequence exhibits sequence correlation to mammalian, plant, and several viral proteins. Injection of synthetic analogs into mosquitoes, biting midges, flies, and fleas inhibited proteolytic enzyme biosynthesis in the midgut. Binding studies with [3H]oostatic factor indicated that the midgut epithelial cells have a factor-specific receptor.

Aedes↗
PubMed1990

Methodology of ECG interpretation in the Hannover program.

The Hannover ECG program HES has been designed for measurement and interpretation of resting and (moderate) exercise electrocardiograms. In the signal analysis part the program follows an averaging strategy. For diagnostic classification a hybrid model with decision trees and scoring algorithms, and with multivariate probabilistic tests for derivation of category A statements is applied. The multivariate classification technique allows to adjust sensitivity and specificity for specific application areas without changing the diagnostic criteria.

Algorithms↗
PubMed1990

Contextual constraints on memory retrieval at six months.

In 3 experiments, 6-month-old infants learned to move a mobile by kicking and were tested 1 to 21 days later for retention of the newly acquired memory as a function of the training and testing contexts. In Experiment 1, decreasing the relative distinctiveness of the training and testing context did not impair retrieval of the newly acquired memory. In Experiment 2, however, testing in a different context completely eliminated retention after delays of 1 and 3 days, when retention was otherwise perfect; after progressively longer delays, retention improved paradoxically. The familiarity or novelty of the test context was not a factor in the failure of infants to recognize the mobile in the altered context after 1 day. In Experiment 3, the effect of an altered context was assessed in a reactivation paradigm. After the training memory was forgotten, infants were presented with the original mobile as a reminder and were tested for retention of the training memory 1 day later. When either the reminding context or the testing context was different, they exhibited no retention. These findings reveal that memory retrieval at 6 months is highly specific to the setting in which the memory is acquired. We propose that infants learn what specific events are associated with what specific places prior to the age when they can locomote independently and acquire a spatiotemporal map of the relations between those places.

Attention↗
PubMed1988

Continuities in infant memory development.

Fifty-five 6- to 7-month-old human infants were trained in an operant conditioning procedure, adapted from a procedure developed for 3-month-olds, in which kicks were reinforced by conjugate movement of a mobile. Retention was assessed in a simple forgetting paradigm (Expt. 1) or in a reactivation paradigm (Expt. 2) with either the training mobile or a different one serving as the retrieval cue. In Experiment 1, retention was tested 1, 7, 14, or 21 days after training. When the training and test mobiles were the same, infants exhibited virtually no forgetting for 14 days, but forgetting was complete by 21. When the training and test mobiles were different, infants exhibited no retention, discriminating the novel mobile for as long as they could remember the contingency. In Experiment 2, when the training mobile was presented as a reminder, the forgetting previously seen after 21 days was alleviated; when a different mobile was the reminder, it was not. These findings reveal that the efficacy of a reminder is predicted by the efficacy of that same stimulus in cuing the original memory 24 hr following training. Although the 6-month-olds learned more rapidly and remembered longer than infants half their age, their memory processing was described by the same basic principles.

Child Development↗
PubMed1987

Trypsin and chymotrypsin-like enzymes of the sandfly Phlebotomus papatasi infected with Leishmania and their possible role in vector competence.

Phlebotomus papatasi (Scopoli) is susceptible to infection with Leishmania major Yakimov & Schokov and resistant to L. donovani Laveran & Mesnil. The possibility that susceptibility depends on midgut levels of trypsin and chymotrypsin-like (esterolytic) enzymes was investigated. Infection with L. major reduced the trypsin-like activity to 93.5% and 86% of the control value at 20 and 30 h post feeding and increased it to 106% at 52 h. Infection with L. donovani reduced trypsin-like activity to 64% and 73% of the control value at 30 and 52 h post feeding. The overall amount of trypsin and chymotrypsin-like enzymes in L. major infections was reduced to 50% and 34% of the control value at 20 and 30 h post feeding and increased to 184% at 52 h. Only one of the enzymes separated by gel electrophoresis was lower throughout, i.e. peak D. Overall, the midgut enzyme level with L. donovani infection was 86% of the control value at 30 h post feeding and 105% at 52 h; their relative amounts changed throughout. Soybean trypsin inhibitor enabled L. donovani to survive and multiply in P. papatasi. It is suggested that a specific component of the trypsin-like activity prevents the survival of L. donovani in P. papatasi and that modulation of this factor enables L. major to survive.

Animals↗
PubMed1987

Polycyclic aromatic compounds as phototoxic mosquito larvicides.

The phototoxicity of 2-acetylnaphthalene, 1-acetylnaphthalene, 1-naphthalenecarboxaldehyde, 9-xanthenone, 9-thioxanthenone, 9-methylanthracene, anthracene, alpha-terthienyl, pyrene and fluoranthene was tested with larvae of Aedes aegypti, Ae. taeniorhynchus and Culex quinquefasciatus. The larvae were exposed to the chemicals in the presence of sunlight for intervals from 1 to 6 hr and the corresponding LC50 values calculated. The LC50 values determined when the 6-hr exposure was followed by 18 hr in the dark range from over 10 ppm to below 0.001 ppm. Naphthalene derivatives were the least active while alpha-terthienyl, anthracene, 9-methylanthracene, pyrene and fluoranthene were the most phototoxic.

Animals↗
PubMed1976

On the mechanism of amylose branching by potato Q-enzyme.

1. When potato Q-enzyme converts amylose into an amylopectin-like molecule, the action is by a random, endo-type transglycosylation of the substrate chains. 2. Inter-chain transfer takes place during the formation of the amylopectin branch linkage. This is seen in experiments in which radioactive label was transferred between substrates of disparate molecular weight. Intra-chain transfer, leading to the formation of a branch linkage, is not excluded by these experiments. 3. The minimum length of amylose chain that can act as an acceptor in the transglycosylation reaction, under the experimental conditions described, is greater than 40 glucose units. 4. The requirement of Q-enzyme for substrate chains at least 40 glucose units in length is interpreted as meaning that a stabilized secondary and tertiary structure must be established in the substrate before it can be utilized by Q-enzyme, and that the forces that provide such conformation are sufficiently strong only when the chains are longer than the minimum. Inter-chain transfer is seen as taking place by one of two mechanisms. The first involved the reaction of the enzyme with a chain that has a stabilized (helical?) conformation. An enzyme-donor chain intermediate is formed, that then reacts with an acceptor chain to complete the transglycosylation. The second mechanism envisages the substrate for the enzyme as being a complex formed between two chains (a double helix?). The enzyme encounters the complex and carries out an inter-chain transglycosylation reactions.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1975

Purification and properties of potato 1,4-alpha-D-glucan:1,4-alpha-D-glucan 6-alpha-(1,4-alpha-glucano)-transferase. Evidence against a dual catalytic function in amylose-branching enzyme.

Q-Enzyme, the enzyme that synthesizes the 1,6-alpha-glucosidic branch linkages of amylopectin, has been purified from potato to near homogeneity. The molecular weight of the enzyme is 85000. The active enzyme is a monomer, with a molar activity at pH 7.0 and 24 degrees C of 15. The energy of activation is 25 kJ/mol below 15 degrees C, changing sharply to 63 kJ/mol above that temperature. Enzyme activity is not affected by Mg2+ or ATP. There are about 11 readily titratable sulfhydryl groups per molecule. The evidence that the enzyme is a single protein entity, without hydrolytic activity towards amylose, contrasts with an earlier report that Q-enzyme consists of two components, a hydrolase with molecular weight 70000, and a transferase with molecular weight 20000. Q-enzyme acts on native and synthetic amyloses to give products resembling amylopectin in terms of average unit chain length, degress of beta-amylolysis and iodine stain. The profiles of the unit chains of these synthetic products are, however, different from that of native amylopectin. Additional branch linkages are introduced by Q-enzyme into potato amylopectin, but the product bears no resemblance to phytoglycogen.

1,4-alpha-Glucan Branching Enzyme↗