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Biomedical subjects

B Drake

Publications and source records attributed to B Drake.

At least 19 recordsLinked to original sources
PubMed2001

Bone indentation recovery time correlates with bond reforming time.

Despite centuries of work, dating back to Galileo, the molecular basis of bone's toughness and strength remains largely a mystery. A great deal is known about bone microsctructure and the microcracks that are precursors to its fracture, but little is known about the basic mechanism for dissipating the energy of an impact to keep the bone from fracturing. Bone is a nanocomposite of hydroxyapatite crystals and an organic matrix. Because rigid crystals such as the hydroxyapatite crystals cannot dissipate much energy, the organic matrix, which is mainly collagen, must be involved. A reduction in the number of collagen cross links has been associated with reduced bone strength and collagen is molecularly elongated ('pulled') when bovine tendon is strained. Using an atomic force microscope, a molecular mechanistic origin for the remarkable toughness of another biocomposite material, abalone nacre, has been found. Here we report that bone, like abalone nacre, contains polymers with 'sacrificial bonds' that both protect the polymer backbone and dissipate energy. The time needed for these sacrificial bonds to reform after pulling correlates with the time needed for bone to recover its toughness as measured by atomic force microscope indentation testing. We suggest that the sacrificial bonds found within or between collagen molecules may be partially responsible for the toughness of bone.

Animals↗
PubMed2001

Maltreatment perpetrators: a 54-month analysis of recidivism.

OBJECTIVE: This study compared recidivism rates for alleged maltreatment perpetrators whose initial report was substantiated and those whose initial report was not substantiated, to determine whether they returned to the child welfare system at differing rates. METHOD: Statewide administrative child welfare services data over a period of 4 1/2 years was analyzed. The sample included 31,531 perpetrators of intrafamilial maltreatment. Separate analyses were conducted for each type of maltreatment (sexual abuse, physical abuse, and neglect). RESULTS: Bivariate relationships (substantiation status and recidivism) were analyzed using survival curves, and the study found that recidivism patterns differed by type of maltreatment and by substantiation status at the index event. Multivariate analyses using Cox Proportional Hazards models found that bivariate relationships held true even when controlling for neighborhood mean income, ethnicity, and gender. CONCLUSIONS: The study's finding that perpetrators whose index event was not substantiated return to the child welfare system at a high rate suggests the need to learn how to discriminate those unsubstantiated alleged perpetrators who are most at risk for recidivism. The finding of frequent cross-type recidivism indicates that intervention should focus on common themes across maltreatment types.

Adolescent↗
PubMed2000

Substantiation and early decision points in public child welfare: a conceptual reconsideration.

This article will overview substantiation in the context of early intervention decision points faced in state child welfare. The conceptual complexities underlying these interventions and how substantiation does or does not play a role in these interventions are explored. Specific attention will be given to the voluntary or involuntary nature of services, the availability of evidence, and the past or future orientation of the decision-making process. The conceptual consistency of recent child welfare policies will be explored, and suggestions for policy and research will be put forward.

Child↗
PubMed1999

Decreased leaf-miner abundance in elevated CO2: reduced leaf quality and increased parasitoid attack.

Most studies on the effects of elevated CO2 have focused on the effects on plant growth and ecosystem processes. Fewer studies have examined the effects of elevated CO2 on herbivory, and of these, most have examined feeding rates in laboratory conditions. Our study takes advantage of an open-top CO2 fertilization study in a Florida scrub-oak community to examine the effects of elevated CO2 on herbivore densities, herbivore feeding rates, and levels of attack of herbivores by natural enemies. Higher atmospheric CO2 concentration reduced plant foliar nitrogen concentrations, decreased abundance of leaf-mining insect herbivores, increased per capita leaf consumption by leafminers, and increased leafminer mortality. As suggested by other authors, reduced foliar quality contributed to the increase in herbivore mortality, but only partly. The major factor increasing mortality was higher attack rate by parasitoids. Thus increasing CO2 concentrations may reduce the survivorship of insect herbivores directly, by reducing plant quality, but also indirectly, by changing herbivore feeding and eliciting greater top-down pressure from natural enemies.

Animals↗
PubMed1998

Dormancy-associated gene expression in pea axillary buds. Cloning and expression of PsDRM1 and PsDRM2.

Pea (Pisum sativum L. cv. Alaska) axillary buds can be stimulated to cycle between dormant and growing states. Dormant buds synthesize unique proteins and are as metabolically active as growing buds. Two cDNAs, PsDRM1 and PsDRM2, were isolated from a dormant bud library. The deduced amino acid sequence of PsDRM1 (111 residues) is 75% identical to that of an auxin-repressed strawberry clone. PsDRM2 encodes a putative protein containing 129 residues, which includes 11 repeats of the sequence [G]-GGGY[H][N] (the bracketed residues may be absent). PsDRM2 is related to cold- and ABA-stimulated clones from alfalfa. Decapitating the terminal bud rapidly stimulates dormant axillary buds to begin growing. The abundance of PsDRM1 mRNA in axillary buds declines 20-fold within 6 h of decapitation; it quickly reaccumulates when buds become dormant again. The level of PsDRM2 mRNA is about three fold lower in growing buds than in dormant buds. Expression of PsDRM1 is enhanced in other non-growing organs (roots >> root apices; fully-elongated stems > elongating stems), and thus is an excellent "dormancy" marker. In contrast, PsDRM2 expression is not dormancy-associated in other organs.

Amino Acid Sequence↗
PubMed1998

Bias in child maltreatment reporting: revisiting the myth of classlessness.

Data on the degree of class bias in child protective services databases are reviewed, along with recent empirical findings on the class distribution of child maltreatment. The evidence suggests high levels of child abuse and neglect among the poor and, despite debate on the question, there is no body of empirical data suggesting that these findings are a product of bias predisposing toward overestimates of child maltreatment among the poor. Implications for research, practice, and policy are offered.

Bias↗
PubMed1996

Understanding the relationship between neighborhood poverty and specific types of child maltreatment.

In this paper we examined the relationship between neighborhood poverty and three different types of child maltreatment; neglect, physical abuse, and sexual abuse. We explore both rates of reporting and rates of substantiated reports across low, moderate, and high poverty areas. We use 1990 Census data and Child Protective Services (CPS) data to study this relationship. We find that neighborhood poverty is positively associated with all three forms of child maltreatment, but to different degrees. Of the three types of child maltreatment, child neglect is most powerfully associated with neighborhood poverty status.

Adolescent↗
PubMed1995

Imaging real-time neurite outgrowth and cytoskeletal reorganization with an atomic force microscope.

An atomic force microscope was used to image the morphology and structural reorganization of rat NIH/3T3 fibroblasts and PC-12 cells growing in petri dishes. NIH/3T3 fibroblasts had a uniform morphology and an extensive cytoskeletal network. Cell thickness varied from approximately 2-3 microns above the nucleus to approximately 20-30 nm over the distal processes, and cytoskeletal fibers as small as 30 nm wide were observed. Imaging over an extended period of time showed a limited degree of cytoskeletal reorganization. Localized force dissection did not induce significant retraction of cellular processes and immediate cell death. Differentiating PC-12 cells with a neuronal phenotype had a nonuniform morphology, abundant cytoskeletal elements, neuritic processes, and growth cones. The cell thickness varied from approximately 5-8 microns over the nucleus to approximately 100-500 nm over the neuritic processes; growth cones approximately 50-700 nm wide and end structures approximately 30-150 nm wide were visible. Repeated imaging showed reorganization of the growth cone, especially the appearance and disappearance of beadlike features and fibrous organization. Thus an atomic force microscope can be used for high-resolution real-time studies of the dynamic subcellular mechanisms that drive cell behavior.

3T3 Cells↗
PubMed1994

Atomic force microscopy and molecular modeling of protein and peptide binding to calcite.

Oyster shell protein and polyaspartate bound to calcite have been visualized at the atomic and molecular levels by atomic force microscopy. The identities of potential binding sites have been suggested from atomic force microscopy (AFM) images and have been evaluated by molecular modeling. Energies and conformations of binding to (110) and (110) prism faces, (001) basal calcium planes, and (104) cleavage planes are considered. The interaction with the basal plane is strongest and is essentially irreversible. Binding to (110) prism surfaces is also energetically favored and selective for orientations parallel or perpendicular to the c-axis. Binding to (110) faces is significantly weaker and orientation nonspecific. If carboxyl groups of the protein or peptide replace select carbonate ions of the (110) face, the binding energy increases significantly, favoring binding in the parallel direction. Binding to (104) cleavage surfaces is weak and probably reversible. Specific alignment of oyster shell protein molecules on calcite surfaces is shown by AFM, and the relevance to the binding model is discussed.

Animals↗
PubMed1994

Motion and enzymatic degradation of DNA in the atomic force microscope.

The dynamics and enzymatic degradation of single DNA molecules can now be observed with the atomic force microscope. A combination of two advances has made this possible. Tapping in fluid has reduced lateral forces, which permits the imaging of loosely adsorbed molecules; and the presence of nickel ions appears to form a relatively stable bridge between the negatively charged mica and the negatively charged DNA phosphate backbone. Continuous imaging shows DNA motion and the process of DNA degradation by the nuclease DNase I. It is possible to see DNase degradation of both loosely adsorbed and tightly adsorbed DNA molecules. This method gives images in aqueous buffer of bare, uncoated DNA molecules with lengths of only a few hundred base pairs, or approximately 100 nm in length.

Adsorption↗
PubMed1994

Relationship competencies in child welfare services.

A series of nine focus groups were conducted to obtain worker and client views of key competencies in child welfare services. Both clients and workers cited the worker's ability to establish an effective working relationship as the primary prerequisite to effective assessment or intervention. A range of specific worker-client relationship competencies are identified and discussed, as are implications of the findings for social work practice, training, and education.

Child↗
PubMed1993

A COOH-terminal peptide confers regiospecific orientation and facilitates atomic force microscopy of an IgG1.

An antibody (IgG1) was designed for oriented adherence to a metal-containing surface. This was achieved by adding a metal-chelating peptide, (CP = His-Trp-His-His-His-Pro), to the COOH-terminus of the heavy chain through genetic engineering. Electroporation of the engineered heavy chain gene into cells expressing the complimentary light chain yielded colonies secreting an intact antibody containing the metal-chelating peptide (IgG1-CP) which had high affinity for a nickel-loaded iminodiacetate column. Purified IgG1-CP was bound to nickel-treated mica and imaged by atomic force microscopy (AFM). Antibody lacking the COOH-terminal metal binding peptide failed to produce discernible AFM images. The AFM images of individual IgG1-CP molecules and their calculated dimensions demonstrated that regiospecific binding and uniform orientation of the antibody was imparted by the peptide. The ability to stably orient macromolecules in their native state to a surface may be used advantageously to visualize them.

Amino Acid Sequence↗
PubMed1990

Decidua-associated suppressor activity and viability of individual implantation sites of allopregnant C3H mice.

Release of soluble suppressor activity from individual implant site decidua of DBA/2-mated C3H/HeJ mice was measured on days 12.5-13.5 of pregnancy. Suppressor activity varied among sites and followed a distribution curve that was displaced towards low suppression when resorption sites were compared to healthy embryonic implants. Pre-immunization against the DBA/2 strain paternal antigens failed to increase resorption (by loss of low suppression implants) but led instead to a reduced resorption rate. This was associated with an increase in soluble suppressor activity obtained from decidua. Some reduction in resorption occurred independent of an increase in the level of suppression suggesting additional contributing factors to the immunization effect.

Animals↗