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Biomedical subjects

R D Harris

Publications and source records attributed to R D Harris.

At least 91 records · Page 5Linked to original sources
PubMed1986

Temperature dependence of length of elastin and its polypentapeptide.

Comparison of the temperature dependence of elastomer length of the cross-linked protein, elastin, and of gamma-irradiation cross-linked poly(VPGVG), the polypentapeptide of elastin, with that of latex rubber demonstrate markedly dissimilar behaviors between a classical rubber and the protein and polypeptide elastomers. In the absence of a load latex rubber expands with increasing temperature as is known for classical rubbers comprised of a network of random chains whereas the protein and polypeptide elastomers markedly decrease in length. When under load with a constant applied force, as a classical rubber, latex linearly decreases length with increasing temperature whereas the decrease in length is very non-linear with temperature increase for the protein and polypeptide elastomers. The protein and polypeptide elastomers examined here do not exhibit the characteristic and fundamental temperature dependence of length considered typical of networks of random chains. Accordingly the more complex and even inverse behavior of elastin and the polypentapeptide of elastin in the absence of load require consideration of structural perspectives different from those of a random chain network with negligible interchain interactions.

Amino Acid Sequence↗
PubMed1986

The Beirut terrorist bombing.

The Beirut terrorist bombing on October 23, 1983, caused 234 immediate deaths and injured at least 112 survivors. Military medical records were available for each casualty; postmortem examination reports were available for each immediate fatality. This represented a unique opportunity to assess type, incidence, treatment, and outcome of neurological injuries suffered in a mass casualty terrorist bombing situation. Three categories of neurological injuries are described: head injuries, spine and spinal cord injuries, and peripheral nerve injuries. The following types and numbers of injuries occurred among the 112 immediate survivors of the explosion: 37 head injuries--28 concussions, 20 scalp lacerations, 13 skull fractures, 6 facial bone fractures, 4 cerebral contusions, 5 dural lacerations, 2 cerebrospinal fluid fistulas, and 2 intracerebral hematomas; 2 spine or spinal cord injuries--1 cervical and 1 thoracolumbar spine fracture associated with neurological deficit; and 9 peripheral nerve injuries--1 facial nerve palsy, 2 brachial plexus palsies, 1 median and 1 radial nerve palsy, and 4 peroneal nerve palsies. Among 234 immediate fatalities, the types and numbers of neurological injuries were: 167 head injuries--93 scalp lacerations, 85 skull fractures, and 24 facial bone fractures; and 22 spine and spinal cord injuries--15 cervical and 7 thoracolumbar fractures. Seven of the 112 immediate survivors died; 4 of these deaths were related to severe head injuries. The treatment and outcome of survivors with neurological injuries is briefly described. One-third of the immediate survivors who suffered either a scalp laceration or a concussion had a concomitant skull fracture.(ABSTRACT TRUNCATED AT 250 WORDS)

Blast Injuries↗
PubMed1986

Unusual metastasis to the cauda equina: case report.

A case of intradural metastasis from endometrial carcinoma to the cauda equina is presented. The clinical presentation and radiographic findings were misleading and suggested a herniated nucleus pulposus. Findings at operation were most suggestive of an ependymoma, but final pathological diagnosis revealed endometrial carcinoma. This has never been reported. Once again it demonstrates that surgeons managing lumbar disc disease must be prepared for possible intradural exploration with an appropriate team.

Adenocarcinoma↗
PubMed1986

Polytetrapeptide of elastin. Temperature-correlated elastomeric force and structure development.

High molecular weight polytetrapeptide of elastin, (L.Val1-L.Pro2-Gly3-Gly4)n, was synthesized using activation of the (GGVP) permutation for polymerization. The temperature-dependence of aggregation was characterized as a function of concentration and the circular dichroism spectra were obtained in the 20 degrees to 70 degrees C temperature range. The latter showed an inverse temperature transition centered near 50 degrees C in which polypeptide order increased on raising the temperature. A concentration of 0.6 g of polytetrapeptide in 1 g of water was gamma irradiation cross-linked (20 Mrad) to form an elastomeric matrix. A study of the temperature-dependence of elastomeric force demonstrated a transition toward increased force on raising the temperature with a midpoint of the transition near 50 degrees C. Thus, there is a correlation between increase in intramolecular order and elastomeric force development. These results are compared to previous results on the polypentapeptide of elastin, (VPGVG)n and on an analog, (IPGVG)n, to demonstrate that the temperature of the transition is proportional to the hydrophobicity of the repeating unit. The point is noted that the elastomeric force development correlates better with intramolecular ordering than with intermolecular processes.

Amino Acid Sequence↗
PubMed1985

Portable ultrasound examinations in intensive care units.

The portability of modern real-time ultrasound units has led to a marked increase in the demand for examinations in medical, surgical, and pediatric intensive care units, the pediatric nursery, and the operating room. The results of all portable ultrasound examinations in the medical and surgical intensive care units at the Massachusetts General Hospital over a four-month period were analyzed to determine the efficacy of such studies. Of 48 examinations, portable sonograms were useful in 90 per cent, found new, clinically important information in 17 per cent, and led to misleading information in 4 per cent. Portable ultrasound examinations are valuable clinically and are probably cost effective.

Boston↗
PubMed1984

Polypentapeptide of elastin: temperature dependence correlation of elastomeric force and dielectric permittivity.

The polypentapeptide of elastin, (L X Val1-L X Pro2-Gly3-L X Val4-Gly5)n, when gamma-irradiation cross-linked in the coacervate state, is shown by means of thermoelasticity data to be a relatively simple system on which to study polypeptide elasticity. Strikingly, the temperature dependence of the elastomeric force exhibited by cross-linked polypentapeptide coacervate is shown to be proportional to the temperature dependence of the dielectric permittivity of the polypentapeptide coacervate over the critical temperature range of 25 degrees C to 55 degrees C where the force increases five fold. This demonstrates that the mobility of dipolar elements are in large part responsible for the elastomeric force and that dielectric relaxation studies contain the potential for identifying the nature of the dynamic elements responsible for bioelasticity.

Chemical Phenomena↗
PubMed1984

Shortened analog of the gramicidin A channel argues for the doubly occupied channel as the dominant conducting state.

A shortened analog of the gramicidin A transmembrane channel has been synthesized and its transport characterized in planar lipid bilayer membranes. General considerations of a shorter diffusional length and a shorter distance over which the voltage drop occurs (i.e., an increased electric field) would contribute to an increase in single-channel conductance. The finding of a decreased single-channel conductance supports the perspective that the dominant conducting state is the doubly occupied channel wherein distance-dependent repulsion due to the first ion in the channel impedes entry of the second ion in the shorter channel.

Amino Acid Sequence↗
PubMed1984

Dispersity of des-L X Val7-D X Val8-Gramicidin A single channel conductances argues for different side chain orientations as basis.

Planar bilayer studies are reported on the channel activity of des-L X Val7-D X Val8-Gramicidin A. This analog is designed to provide more long-lived side chain distributions involving the Trp residues than occur with Gramicidin A. The carbonyls of these residues coordinate the permeant cation and the energetics of the coordination, which is proposed to depend on side chain orientation, determines the free energies of the rate limiting entrance-exit barriers and the binding sites. The finding of an increased dispersity of single channel conductance for the analog supports the perspective that dispersity derives from different side chain distributions on the same backbone conformation. Channel mechanism is not understood until dispersity is explained.

Electric Conductivity↗
PubMed1984

Temperature dependence of single channel currents and the peptide libration mechanism for ion transport through the gramicidin A transmembrane channel.

A study of the temperature dependence of gramicidin A conductance of K+ in diphytanoyllecithin/n-decane membranes shows the plot of In (single channel conductance) as a function of reciprocal temperature to be nonlinear for the most probable set of conductance states. These results are considered in terms of a series of barriers, of the dynamics of channel conformation, vis-a-vis the peptide libration mechanism, and of the effect of lipid viscosity on side chain motions again as affecting the energetics of peptide libration.

Gramicidin↗
PubMed1984

Renal arterial injury associated with percutaneous nephrostomy.

A case of pseudoaneurysm and subcapsular hematoma as a complication of a percutaneous nephrostomy with unusual clinical findings is presented. Bleeding following a closed nephrostomy must be kept in mind as a potential hazard. Computerized tomography (CT) examination should be performed in such cases using intravenous radiographic contrast material whenever possible to identify the potential bleeding site rapidly.

Adult↗
PubMed1984

D X Ala3 analog of elastin polypentapeptide. An elastomer with an increased young's modulus.

The polypentapeptide , H(L X Val1-L X Pro2-D X Ala3-L X Val4- Gly5 )n Val-OMe which is the D X Ala3 analog of the elastomeric polypentapeptide (PPP) of elastin, (L X Val1-L X Pro2-Gly3-L X Val4- Gly5 )n, has been synthesized. Its conformation is compared to that of the PPP and found to be similar with a somewhat stabilized beta-turn. The D X Ala3 analog coacervates to form a more cohesive viscoelastic material and the coacervate when cross-linked by gamma-irradiation exhibits an approximate doubling of the Young's modulus of elasticity. These results are discussed in connection with other related analogs of the polypentapeptide of elastin, which are non-elastomeric, and found to be consistent with a proposed conformationally based librational entropy mechanism of elasticity.

Elasticity↗
PubMed1983

Pyridine nucleotide synthesis in normal and neoplastic human pituitary cells in culture.

14C-Nicotinic acid (NA) incorporation into nicotinamide adenine dinucleotide (NAD) was studied in cultures from 7 normal human pituitaries and 13 chromophobe adenomas. 14C-NA (7.2 microM) was incubated with both normal and tumor cell cultures for periods up to 48 hours. Cells and culture media were examined separately for metabolites at 24 and 48 hours. NAD was the major labeled metabolite found in both normal and tumor cells, accounting for 65.4% for normal cells and 56.8% for tumor cells of the total cellular label at 48 hours. Nicotinamide (NAm), a product arising from NAD, was the only labeled metabolite found in the culture medium, aside from the 14C-NA added initially. Total incorporation of 14C-NA into NAD was estimated by adding the cellular 14C-NAD and labeled products of NAD (NMN, NAm and NADP) to the 14C-NAm found in the medium for each culture. Cultures derived from adenomas demonstrated greater than twice the rate of incorporation of 14C-NA into NAD as did normal cell cultures (P less than 0.01 at 24 hours and less than 0.001 at 48 hours). This difference did not appear to be related to the secretory status of the tumor, since both secreting and nonsecreting tumors demonstrated increased rates when compared to normal cells. This difference also persisted in two different culture media and with cells that had been maintained in culture for different lengths of time (6-day dispersed cell cultures and 6- to 16-week fragment cultures).

Adenoma, Chromophobe↗
PubMed1983

D-Ala5 analog of the elastin polypentapeptide. Physical characterization.

The D-Ala5 analog, (L-Val1-L X Pro2-Gly3-L X Val4-D-Ala5) of the polypentapeptide (PPP) of elastin is synthesized and characterized by a series of physical methods. Carbon-13 and proton nuclear magnetic resonance spectroscopies are used to verify purity and, by means of solvent dependence of peptide C-O chemical shift and of temperature dependence of peptide NH chemical shift, to establish by comparison with the PPP of elastin the presence and increased stability of the Type II Pro2-Gly3 beta-turn. The temperature dependence of aggregation in water to form a viscoelastic phase called the coacervate is reported for several concentrations. Comparison of carbon-13 nuclear magnetic resonance spectra obtained under identical conditions for the coacervate states of the PPP of elastin and the D-Ala5 analog shows the effect of replacing the Gly5 residue by a D-Ala5 residue to be one of greatly restricting mobility of the polypeptide chain. Scanning electron micrographs, of the coacervate alone and of the coacervate cross-linked and compounded to a Dacron fabric before and after stress-strain studies, are reported which show the D-Ala5 PPP matrix to rupture during the stresses of drying and of stretching while wet. Thus, the effect of adding a methyl moiety to the Gly5 residue of the PPP of elastin is to decrease markedly the mobility of the polypeptide chain and to destroy elasticity. The results are presented as a test of the proposed librational entropy mechanism of elasticity of the PPP of elastin.

Crystallization↗