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Biomedical subjects

J A Bennett

Publications and source records attributed to J A Bennett.

At least 19 recordsLinked to original sources
PubMed2004

Synthetic peptide derived from alpha-fetoprotein inhibits growth of human breast cancer: investigation of the pharmacophore and synthesis optimization.

Asynthetic peptide that inhibits the growth of estrogen receptor positive (ER+) human breast cancers, growing as xenografts in mice, has been reported. The cyclic 9-mer peptide, cyclo[EMTOVNOGQ], is derived from alpha-fetoprotein (AFP), a safe, naturally occurring human protein produced during pregnancy, which itself has anti-estrogenic and anti-breast cancer activity. To determine the pharmacophore of the peptide, a series of analogs was prepared using solid-phase peptide synthesis. Analogs were screened in a 1-day bioassay, which assessed their ability to inhibit the estrogen-stimulated growth of uterus in immature mice. Deletion of glutamic acid, Glu1, abolished activity of the peptide, but glutamine (Gln) or asparagine (Asn) could be substituted for Glu1 without loss of activity. Methionine (Met2) was replaced with lysine (Lys) or tyrosine (Tyr) with retention of activity. Substitution of Lys for Met2 in the cyclic molecule resulted in a compound with activity comparable with the Met2-containing cyclic molecule, but with a greater than twofold increase in purity and corresponding increase in yield. This Lys analog demonstrated anti-breast cancer activity equivalent to that of the original Met-containing peptide. Therefore, Met2 is not essential for biologic activity and substitution of Lys is synthetically advantageous. Threonine (Thr3) is a nonessential site, and can be substituted with serine (Ser), valine (Val), or alanine (Ala) without significant loss of activity. Hydroxyproline (Hyp), substituted in place of the naturally occurring prolines (Pro4, Pro7), allowed retention of activity and increased stability of the peptide during storage. Replacement of the first Pro (Pro4) with Ser maintains the activity of the peptide, but substitution of Ser for the second Pro (Pro7) abolishes the activity of the peptide. This suggests that the imino acid at residue 7 is important for conformation of the peptide, and the backbone atoms are part of the pharmacophore, but Pro4 is not essential. Valine (Val5) can be substituted only with branched-chain amino acids (isoleucine, leucine or Thr); replacement by d-valine or Ala resulted in loss of biologic activity. Thus, for this site, the bulky branched side chain is essential. Asparagine (Asn6) is essential for activity. Substitution with Gln or aspartic acid (Asp), resulted in reduction of biologic activity. Removal of glycine (Gly8) resulted in a loss of activity but nonconservative substitutions can be made at this site without a loss of activity indicating that it is not part of the pharmacophore. Cyclization of the peptide is facilitated by addition of Gln9, but this residue does not occur in AFP nor is it necessary for activity. Gln9 can be replaced with Asn, resulting in a molecule with similar activity. These data indicate that the pharmacophore of the peptide includes side chains of Val5 and Asn6 and backbone atoms contributed by Thr3, Val5, Asn6, Hyp7 and Gly8. Met2 and Gln9 can be modified or replaced. Glu1 can be replaced with charged amino acids, and is not likely to be part of the binding site of the peptide. The results of this study provide information that will be helpful in the rational modification of cyclo[EMTOVNOGQ] to yield peptide analogs and peptidomimetics with advantages in synthesis, pharmacologic properties, and biologic activity.

Amino Acid Sequence↗
PubMed2002

Gene frequencies of human platelet antigens 1-5 in indigenous Australians in Western Australia.

The frequencies of human platelet antigen (HPA) systems vary between different racial groups; however, HPA frequency data for some racial groups are still incomplete. We report the distribution of HPA 1-5 systems in Australian Aborigines from a remote community in the north-west of Australia and compare our findings with HPA observed in a Western Australian blood donor population. Using a polymerase chain reaction (PCR) with sequence-specific primers, 185 indigenous Australians and 1000 Western Australian blood donors were genotyped for each of the HPA 1-5 systems. Comparison of gene frequencies of alleles from HPA-1, -2, -3 and -5 systems showed significant differences between Aboriginal people and Western Australian blood donors (P < 0.001). In particular, the frequency of HPA-3b (0.068) in the Australian Aboriginals, from this study, was one of the lowest reported, whilst the frequency of HPA-5b (0.246) was one of the highest for this allele. Gene frequencies were similar to those reported for central Australian Aborigines but with no other ethnic group. In conclusion, this study confirms significant differences in HPA distributions between indigenous Australians, Australian blood donors and other racial groups. These results indicate a higher potential risk of alloimmunization to HPA-1, -2 and -3 in Australian Aborigines receiving transfusion therapy from a Caucasian blood donor population, thereby having practical implications for transfusion and pregnancy risks in people of Aboriginal origin.

Antigens, Human Platelet↗
PubMed2001

Two new loci affecting cell division identified as suppressors of an ftsQ-null mutation in Streptomyces coelicolor A3(2).

Mutations in fts genes partially or completely block both vegetative cell division and sporulation septation in the filamentous bacterium Streptomyces coelicolor A3(2). Using a novel screen, we independently isolated two double-mutant strains, each containing a spontaneous suppressor mutation, which partially restores division to an ftsQ-null mutant. Genetic complementation experiments revealed that the suppressor mutations alone confer no observable defect in sporulation. The suppressor mutations were genetically mapped to regions of the chromosome, distinct from each other and the division and cell wall cluster containing ftsQ. Therefore, the genes identified by the suppressor mutations were named sqnA and sqnB (suppressor of ftsQ-null) and may be representatives of a novel class of genes involved in cell division or the regulation of cell division in this mycelial organism.

Bacterial Proteins↗
PubMed2001

Studies on a growth-inhibitory peptide derived from alpha-fetoprotein and some analogs.

A 34-amino acid synthetic peptide was derived from the third domain of human alpha-fetoprotein, and the peptide was shown to inhibit estrogen-stimulated growth. Under certain conditions, however, the peptide lost growth-inhibitory activity. A biophysical study of the peptide was undertaken with a goal of obtaining completely reliable preparations. The peptide was studied using gel-filtration column chromatography as a function of peptide concentration and age of solution, and was found to exhibit complex aggregation behaviors. During the early period (0-3 h) after dissolving lyophilized peptide into pH 7.4 buffer, solutions were composed mostly of trimers. At higher peptide concentrations (> or = 3.0 g/L), the trimers aggregated extensively to a large aggregate (minimum size approximately 102 peptides). At 5.0-8.0 g/L, these large aggregates increased in size (up to approximately 146 peptides) until trimers were largely exhausted from solution. During the later times (>3 h) after sample preparation, the trimeric oligomer of the peptide dissociated slowly to form dimers for samples at 0.10-3.0 g/L. After their build-up, a very small number of dimers associated to form hexamers. Disulfide bonds stabilized the dimers as indicated by the conversion of dimers to trimers upon the addition of a reducing agent, and the failure of dimers to form in the presence of reducing agent. Reducing agent did not affect trimer or large aggregate formation. Trimers were found to be active in an assay monitoring inhibition of estrogen-stimulated growth, whereas dimers and large aggregates were inactive. The two cysteines in the peptide were modified to either S-methylcysteine or S-(2-aminoethyl)cysteine, and both derivatives showed significant growth-inhibition activity. A serine analog in which both cysteines were replaced had very different aggregation behavior than the cysteine peptide and lacked its growth inhibitory ability. Peptide aggregation is critically important in establishing the ability of the peptide to inhibit growth and have anticancer activity, but the state of its two cysteines is of little influence.

Acetylcysteine↗
PubMed2001

Studies on analogs of a peptide derived from alpha-fetoprotein having antigrowth properties.

A 34-amino acid portion of the third domain of alpha-fetoprotein possesses antigrowth and anticancer activities. Three analogs of this sequence were chemically synthesized, in which the two cysteines of the original sequence were replaced by alanines, glycines or serines. The original cysteine and alanine peptides formed trimers at 0.20 g/L in pH 7.4 phosphate buffer, and the glycine and serine peptides formed dimers. Trimer preparations were more potent in inhibiting estrogen-induced growth in the mouse uterine assays than the two dimeric oligomers. Of salient importance is that the alanine peptide retained its trimeric form in solution much longer than the cysteine peptide. Antigrowth assays were performed starting with stock solutions at a peptide concentration of 0.20 g/L, because at very high peptide concentration (8.0 g/L) the peptides aggregated extensively. All the peptides, although differing in biological activity, had almost identical secondary structures. Unlike alpha-fetoprotein, the three peptides have low amounts of alpha-helix. Trifluoroethanol has the ability to convert peptides into a helical conformation when they have a propensity for that structure. At trifluoroethanol concentrations of 20% and higher, the alanine and glycine peptides were changed into highly helical structures.

Alanine↗
PubMed2001

Development of a synthetic cyclized peptide derived from alpha-fetoprotein that prevents the growth of human breast cancer.

The peptide, EMTPVNPG, derived from alpha-fetoprotein, inhibits estrogen-stimulated growth of immature mouse uterus and estrogen-dependent proliferation of human breast cancer cells. However, the biological activities of the peptide diminish over time in storage, even when in the lyophilized state, probably because of peptide aggregation through hydrophobic interaction among monomers. Two analogs of EMTPVNPG were designed with the intent of minimizing aggregation and retaining biological activity during prolonged storage. EMTOVNOG, where O is 4-hydroxyproline, is a linear peptide generated by substituting 4-hydroxyproline for the two prolines, thereby increasing peptide hydrophilicity. This analog exhibited a dose-dependent inhibition of estrogen-stimulated growth of immature mouse uterus similar to that of EMTPVNPG (maximal activity at 1 microg/mouse). A second analog, cyclo-(EMTOVNOGQ), a hydrophilic, cyclic analog with increased conformational constraint, was as potent as the other peptides in its inhibition of estrogen-dependent growth of immature mouse uterus, and had an expanded effective dose range. Both linear and cyclized hydroxyproline-substituted analogs exhibited indefinite shelf-life. Furthermore, both analogs inhibited the estrogen-dependent growth of MCF-7 human breast cancer growing as a xenograft in SCID mice. These analogs may become significant, novel agents for the treatment of breast cancer.

Amino Acid Substitution↗
PubMed2001

A pilot study of rapid lithium administration in the treatment of acute mania.

OBJECTIVES: The use of rapid lithium dosage administration, a strategy that could lead to rapid improvement in mania, has been largely unexamined. In this open-label, pilot, acute-treatment study, we sought to determine the safety and tolerability of lithium administered at 20 mg/ kg/day. A secondary aim was to provide preliminary data regarding the efficacy of this strategy in ameliorating manic, depressive, and psychotic symptoms. METHODS: Fifteen patients hospitalized with DSM-IV bipolar disorder, manic or mixed, and who provided written informed consent, received lithium 20 mg/kg/day for up to 10 days. Patients were evaluated for adverse effects daily. Lithium levels were obtained on days 2, 3, 4, 5, 7, and 10 or at study termination. Electrocardiograms (EKGs) were performed at baseline and on days 1-5, 7, and 10 or at study termination. Symptomatic improvement was assessed daily using the Young Mania Rating Scale, 24-item Hamilton Depression Rating Scale, and the Scale for Assessment of Positive Symptoms (SAPS). RESULTS: Five of the 15 patients completed the 10-day study period. Two patients dropped out due to adverse events. Seven patients did not complete the inpatient trial because of improvement sufficient to allow hospital discharge. All patients achieved serum lithium concentrations > or =0.6 mEq/L after 1 day of treatment; the mean + SD concentration on day 5 was 1.1 (+/- 0.1) mEq/L on day 5. There were significant reductions from baseline to endpoint on all rating scales, except the SAPS bizarre behavior subscale. CONCLUSIONS: These pilot data suggest that lithium 20 mg/kg/day was well tolerated and that this strategy may produce rapid improvement in affective and psychotic symptoms. These impressions require confirmation in double-blind, randomized trials.

Acute Disease↗
PubMed2001

Reducing waiting times for sleep apnoea hypopnoea syndrome and snoring using a questionnaire and home oximetry: results of a second audit cycle.

As a result of a previous audit on the management of sleep apnoea hypopnoea syndrome (SAHS) which showed long waiting times that were primarily due to unnecessary interspecialty referrals, a change in practice was adopted. All referrals are now sent a questionnaire about symptoms suggestive of SAHS, the Epworth Sleepiness Scale score and their body mass index (BMI) which when returned are categorized into having a high, intermediate or low risk of SAHS. Those patients with a high probability have home overnight oximetry and those with intermediate probability have video oximetry. Those with a low probability are referred directly to ENT. We audited the first 100 patients referred. All were General Practitioner referrals to either ENT or respiratory medicine. Only two patients had a low probability score and were seen directly in ENT. Following sleep study analysis, 10 patients were referred directly to ENT with no respiratory medicine follow-up and nine were discharged back to the General Practitioner with no apnoea or snoring. Eighty-one patients were followed up by respiratory medicine. Of these, 49 received a trial of nasal continuous positive airway pressure (nCPAP) and six were referred to ENT. Therefore the majority justified an investigation to exclude SAHS in the first instance and an unnecessary initial ENT appointment was avoided. We have reduced the average waiting times to sleep study by approximately 90 days and to nCPAP trial by 32 days, mostly due to decreased delays in interspeciality referrrals. We have also demonstrated a greater than 50 per cent reduction in ENT clinic visits, a small increase in the number of sleep studies but no increase in respiratory clinic workload.

England↗
PubMed2000

Alpha-fetoprotein-derived antiestrotrophic octapeptide.

Alpha-fetoprotein (AFP) is a major serum protein produced during fetal development. Experimental findings suggest that AFP has antiestrotrophic activity and that it can be developed as a therapeutic agent to treat existing estrogen-dependent breast cancer or to prevent premalignant foci from developing into breast cancer. The antiestrotrophic activity of AFP was reported to be localized to a peptide consisting of amino acids 447-480, a 34-mer peptide termed P447. A series of parsings and substitutions of amino acids in the P447 sequence was intended to identify the shortest analog which retained antiestrotrophic activity. Peptides related to P447 were generated using solid phase peptide synthesis. Several shorter peptides, including an 8-mer called P472-2 (amino acids 472-479, peptide sequence EMTPVNPG), retained activity, whereas peptides shorter than eight amino acid residues were inactive. The dose-related antiestrotrophic activity of AFP-derived peptides was determined in an immature mouse uterine growth assay that measures their ability to inhibit estradiol-stimulated uterine growth. In this assay, the maximal inhibitory activities exhibited by peptide P472-2 (49%), by peptide P447 (45%), and by intact AFP (35-45%) were comparable. The octapeptide P472-2 was also active against estradiol-stimulated growth of T47D human breast cancer cells in culture. These data suggest that peptide P472-2 is the minimal sequence in AFP, which retains the antiestrotrophic activity found with the full-length molecule. The synthetic nature and defined structure of this 8-mer peptide suggest that it can be developed into a new drug which opposes the action of estrogen, perhaps including the promotional effects of estradiol in the development of human breast cancer.

Amino Acid Sequence↗
PubMed2000

Mediator and moderator variables in nursing research: conceptual and statistical differences.

Mediators and moderators are variables that affect the association between an independent variable and an outcome variable. Mediators provide additional information about how or why two variables are strongly associated. In contrast, moderators explain the circumstances that cause a weak or ambiguous association between two variables that were expected to have a strong relationship. Mediators and moderators are often overlooked in research designs, or the terms are used incorrectly. This article summarizes the conceptual differences between mediators and moderators. The statistical analysis of moderators and mediators in multiple regression is briefly described and two examples are presented.

Humans↗
PubMed2000

Pharmacologic loading in the treatment of acute mania.

The rapid and safe reduction of manic symptoms is an important initial goal of the pharmacologic treatment of acute mania. The pharmacokinetics and studies of pharmacologic loading of lithium, valproate, and carbamazepine were reviewed. In addition, the feasibility of administering other agents with potential efficacy in mania, e.g., atypical antipsychotics and new anticonvulsants, was discussed. Further double-blind, controlled studies with adequate sample sizes comparing loading strategies with more gradual titration schedules of candidate antimanic agents are needed.

Acute Disease↗
PubMed1999

The recombinant third domain of human alpha-fetoprotein retains the antiestrotrophic activity found in the full-length molecule.

Previous studies have shown that alpha-fetoprotein (AFP) interferes with estrogen (E2)-stimulated growth, including E2-stimulated breast cancer growth. In an effort to localize the antiestrotrophic portion of the molecule, the C-terminal one-third (200 amino acids) of human AFP, known as Domain III, was produced in a baculovirus expression system as a fusion protein containing an amino terminal histidine tag. The histidine tag was included to facilitate purification by metal ion affinity chromatography. The purified recombinant Domain III fusion protein was functionally similar to full-length natural AFP isolated from human cord sera or from cultured human hepatoma cells (HepG2) in that they all produced significant and quantitatively similar inhibition of E2-stimulated growth of immature mouse uterus. Furthermore, the dose-response profiles of the recombinant Domain III AFP and natural full-length AFP were similar. Preincubation of either protein in a molar excess of E2 lowered the minimally effective antiestrotrophic dose and produced a difference spectrum consistent with a change in conformation. These findings indicate that the antiestrotrophic activity of AFP is contained within the third domain of the molecule, and they have obvious implications for the production of biologically active peptides derived from this portion of the AFP molecule.

Animals↗
PubMed1999

Dependence of cardiac strength-interval curves on pacing rate.

The purpose of the research is to determine how the pacing rate affects the strength-interval curve in cardiac tissue. Computer simulations are used to calculate the cathodal and anodal strength-interval curves. The tissue is represented by the bidomain model with Beeler-Reuter membrane properties. The strength-interval curves shift to shorter intervals as the pacing rate increases. However, the shape of the strength-interval curve, including the separation into 'make' and 'break' sections and the presence of a 'dip', is insensitive to pacing rate.

Action Potentials↗
PubMed1999

Scintigraphic detection of breast cancer xenografts with Tc-99m natural and recombinant human alpha-fetoprotein.

Because adenocarcinoma of the breast expresses receptors for alpha-fetoprotein (AFP), we studied Tc-99m AFP as a radiopharmaceutical to detect breast cancer. The biodistribution of Tc-99m radiolabeled natural human AFP (full length) and recombinant domain III (DIII) of human AFP was compared to Tc-99m sestamibi and Tl-201 in a murine model of human breast cancer. Estrogen receptor positive (MCF7, T-47D) and estrogen receptor negative (MDA-MB-231, BT-20) human breast cancer xenografts were grown subcutaneously in the lateral thorax region of immunosuppressed mice (ICR SCID). Quantitative comparisons of percent-injected dose per gram of tissue (%ID/gram) and tumor to thigh ratio (T/Th) were performed at 0-60 minutes and at 24 hours following injection. For most tumors, T/Th for AFP and DIII was significantly greater than T/Th for Tc-99m sestamibi and Tl-201. In all breast cancers (BT-20, MCF7, MDA-MB-231, T-47D), Tc-99m AFP T/Th increased from 60 minutes to 24 hours, suggesting good tumor retention of this radiopharmaceutical. DIII and AFP had significantly higher %ID/gram than either Tl-201 or Tc-99m sestamibi when considered across all tumor types at both 60 minutes and 24 hours. The data suggests that localization of Tc-99m AFP in human breast cancer xenografts is initially rapid, increases with time, and is superior to Tc-99m sestamibi and Tl-201. Given its high uptake by breast cancer cells, its low non-tumor localization and its rapid renal excretion, these Tc-99m AFP preparations may be useful agents to detect human breast carcinoma.

Animals↗
PubMed1999

Parent to parent: preventing adolescent exposure to HIV.

A 2-year pilot program implemented by public health nurses (PHNs) in partnership with the leaders of parent associations of 10 urban high schools encouraged communication about health-promoting sexual behavior between adults and adolescents. The purpose was to assess the feasibility of involving parents in health promotion efforts in schools. During the first year, PHNs prepared a cohort of 17 parent trainers to make presentations to parent groups about the reality of teens' risk for human immunodeficiency virus (HIV) exposure, facts to counter myths about outcomes of sex education, and the skills teens need to implement healthy choices, including abstinence, correct condom use, and talking about sex with a potential sexual partner. Each parent trainer was then scheduled to make two presentations at parent association meetings. Criteria for assessing the impact of extending the program, including broader diffusion in the community, are proposed. This approach may be effective for community-based education about other health issues.

Adolescent↗