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PubMed1987

Turnover of cytokeratin polypeptides in mouse hepatocytes.

The turnover of cytokeratin polypeptides A (equivalent to No. 8 of the human cytokeratin catalog) and D (equivalent to human cytokeratin No. 18) of mouse hepatocytes was studied by pulse-labeling of mouse liver proteins after intraperitoneal injection of L-[guanido-14C]arginine and [14C]sodium bicarbonate. At various times after injection cytoskeletal proteins were prepared and separated by SDS-polyacrylamide gel electrophoresis, and the specific radioactivities of polypeptides recovered from excised gel slices were determined. With L-[guanido-14C]arginine a rapid increase in the specific radioactivity of both cytokeratins was observed which reached a plateau between 12 and 24 h. With [14C]sodium bicarbonate maximal specific radioactivity was obtained at 6 h followed by a rapid decrease to half maximum values within the subsequent 6 h and then a slower decrease. Half-lives were determined from the decrease of specific radioactivities after pulse-labeling by least-squares plots and found to be 84 h (for cytokeratin component A) and 104 h (component D) for arginine labeling. Values obtained after bicarbonate labeling were similar (95 h for A and 98 h for D). These results show that liver cytokeratins are relatively stable proteins and suggest that components A and D are synthesized and degraded at similar rates, probably in a coordinate way.

Animals↗
PubMed1990

High-resolution two-dimensional gel analysis of proteins in wing imaginal discs: a data base of Drosophila.

An improved method of high-resolution two-dimensional gel electrophoresis has been used to study the patterns of protein synthesis in wing imaginal discs of late instar larvae of Drosophila melanogaster. A small number of discs were radiolabeled with a mixture of 14C-labeled amino acids or with [35S]methionine and the pattern of labeled proteins was analyzed. One thousand and twenty-five polypeptides (787 acidic (IEF) and 238 basic (NEPHGE] from wing discs of several wild-type strains have so far been separated and cataloged. All these polypeptides have been numbered and presented in a reference map for further studies. When comparing patterns of label we have found small quantitative differences in rate of synthesis between individuals of the same strain, not due to sexual differences, and very few quantitative and qualitative differences between groups of individuals of different strains.

Amino Acids↗
PubMed1987

The mechanical properties of trabecular bone: dependence on anatomic location and function.

In 1961, Evans and King documented the mechanical properties of trabecular bone from multiple locations in the proximal human femur. Since this time, many investigators have cataloged the distribution of trabecular bone material properties from multiple locations within the human skeleton to include femur, tibia, humerus, radius, vertebral bodies, and iliac crest. The results of these studies have revealed tremendous variations in material properties and anisotropy. These variations have been attributed to functional remodeling as dictated by Wolff's Law. Both linear and power functions have been found to explain the relationship between trabecular bone density and material properties. Recent studies have re-emphasized the need to accurately quantify trabecular bone architecture proposing several algorithms capable of determining the anisotropy, connectivity and morphology of the bone. These past studies, as well as continuing work, have significantly increased the accuracy of analytical and experimental models investigating bone, and bone/implant interfaces as well as enhanced our perspective towards understanding the factors which may influence bone formation or resorption.

Biomechanical Phenomena↗
PubMed1988

DNA recognition by the FLP recombinase of the yeast 2 mu plasmid. A mutational analysis of the FLP binding site.

The 2 mu plasmid of the yeast Saccharomyces cerevisiae encodes a site-specific recombination system consisting of the FLP protein and two inverted recombination sites on the plasmid. The minimal fully functional substrate for in-vitro recombination in this system consists of two FLP protein binding sites separated by an eight base-pair spacer sequence. We have used site-directed mutagenesis to generate every possible mutation (36 in all) within 11 base-pairs of one FLP protein binding site and the base-pair immediately flanking it. The base-pairs within the binding site can be separated into three classes on the basis of these results. Thirty of the 36 sequence changes, including all three at seven different positions (class I) produce a negligible or modest effect on FLP protein-promoted recombination. In particular, most transition mutations are well-tolerated in this system. In only one case do all three possible mutations produce large effects (class II). At three positions, clustered near the site at which DNA is cleaved by FLP protein, one of the two possible transversions produces a large effect on recombination, while the other two changes produce modest effects (class III). For seven mutants for which FLP protein binding was measured, a direct correlation between decreases in recombination activity and in binding was observed. Positive effects on the reaction potential of mutant sites are observed when the other FLP binding site in a single recombination site is unaltered or when the second recombination site in a reaction is wild-type. This suggests a functional interaction between FLP binding sites both in cis and in trans. When two mutant recombination sites (each with 1 altered FLP binding site) are recombined, the relative orientation of the mutations (parallel or antiparallel) has no effect on the result. These results provide an extensive substrate catalog to complement future studies in this system.

Base Sequence↗
PubMed1990

Genetic studies of the lac repressor. XIII. Extensive amino acid replacements generated by the use of natural and synthetic nonsense suppressors.

We have altered the amino acid sequence of the lac repressor one residue at a time by utilizing a collection of nonsense suppressors that permit the insertion of 13 different amino acids in response to the amber (UAG) codon, as well as an additional amino acid in response to the UGA codon. We used this collection to suppress nonsense mutations at 141 positions in the lacI gene, which encodes the 360 amino acid long lac repressor, including 53 new nonsense mutations which we constructed by oligonucleotide-directed mutagenesis. This method has generated over 1600 single amino acid substitutions in the lac repressor. We have cataloged the effects of these replacements and have interpreted the results with the objective of gaining a better understanding of lac repressor structure, and protein structure in general. The DNA binding domain of the repressor, involving the amino-terminal 59 amino acids, is extremely sensitive to substitution, with 70% of the replacements resulting in the I- phenotype. However, the remaining 301 amino acid core of the repressor is strikingly tolerant of substitutions, with only 30% of the amino acids introduced causing the I- phenotype. This analysis reveals the location of sites in the protein involved in inducer binding, tighter binding to operator and thermal stability, and permits a virtual genetic image reconstruction of the lac repressor protein.

Amino Acid Sequence↗
PubMed1992

Mapping psychiatric disease genes: impact of new molecular strategies.

Genetic mapping of genes which predispose to psychiatric illness is discussed in relation to recent developments in molecular genetic technology. Among the psychiatric disorders, the mechanism by which genetic factors contribute to illness is poorly understood, and the classification of phenotype (ill-status) is extremely complicated. These uncertainties, together with other complicating factors, tend to undermine the effectiveness of genetic linkage analysis. Two very powerful new molecular strategies have the potential to improve the overall gene mapping effort. First, new applications of polymerase chain reaction (PCR) technology will allow laboratories to generate much more genetic data than has been previously possible. Some of the factors which confound psychiatric linkage analysis should be mitigated by the larger data sets that will be generated with this technology. Second, the cloning of large segments of human chromosomes into yeast artificial chromosomes (YACs) has given rise to strategies to clone and catalog the entire human genome. The goal of constructing overlapping YAC clones (contigs) end-to-end across each human chromosome now appears imminent. This development will have immense effect upon our ability to identify disease genes.

Chromosome Mapping↗
PubMed1996

Cardiac output in normal pregnancy: a critical review.

OBJECTIVE: To review the literature about the effect of normal pregnancy on cardiac output, with special attention to study design, measurement technique, position of the subject, and parity. DATA SOURCES: For studies from the period 1955-1987, we examined Cumulated Index Medicus (National Library of Medicine Cataloging in Publication. Chicago: American Medical Association). For studies from 1988 to May 1, 1994, we used Medline on Silver Platter (U.S. National Library of Medicine Silver Platter International, 1994). METHODS OF STUDY SELECTION: Thirty-three cross-sectional and 19 longitudinal studies on cardiac output measurement in normal pregnancy were retrieved and reviewed. Thirteen longitudinal studies were excluded from analysis because an unvalidated technique was used or because not all subjects were measured at each study interval. The six remaining studies of genuine longitudinal design with at least two measurements throughout pregnancy were used for the definitive analysis. The results of the cross-sectional studies were included only to demonstrate a trend. DATA EXTRACTION AND SYNTHESIS: By pooling data from cross-sectional studies, a tendency was shown toward a higher cardiac output in the second trimester compared with the first trimester, and a tendency toward lower cardiac output was found in the third trimester compared with the second trimester. After delivery, cardiac output was lower than at any time during pregnancy. Selected longitudinal studies showed that the rise in cardiac output occurred early in the first trimester, and a further rise occurred during the second trimester. During the third trimester, cardiac output rose, fell, or plateaued, irrespective of the method of measurement applied or conditions during measurement. CONCLUSIONS: Cardiac output during the third trimester was widely divergent among the studies and probably dependent on individual factors. The tendency to report cardiac output as averages negated these inter-individual differences.

Cardiac Output↗
PubMed1986

Preference of rats for food flavors and texture in nutritionally controlled semi-purified diets.

Preference for nutritionally controlled, semi-purified diets modified by the addition of potent food flavors was determined for Sprague Dawley rats using two-choice diet preference tests. Intake of each food cup was monitored after 1 hr and for each 24 hr period thereafter up to 5 days. Preference was also determined for the flavored diets prepared in three forms differing in texture: powdered, and pellets of two sizes. Rats easily detected minor amounts of the food flavors, and the tests provided a catalog of 12 preferred flavors. Exposure time to the diets altered preference for a minority of flavors; diets initially avoided in the first hour test were likely to become less aversive upon continued exposure. Whether or not a specific flavored diet was preferred, total food intake was not affected during the 5 day period monitored. Rats displayed strong preference for diets of a pelleted texture compared to the same diets in a powdered form.

Animals↗
PubMed1990

Myxoma virus and malignant rabbit fibroma virus encode a serpin-like protein important for virus virulence.

The leporipoxviruses Shope fibroma virus (SFV), the myxoma virus (MYX), and the SFV/MYX recombinant malignant rabbit fibroma virus (MRV) are closely related yet induce profoundly different diseases in the European rabbit. SFV, which produces a benign tumor at the site of inoculation, is cleared by the immune system after approximately 2 weeks whereas MYX and MRV induce a rapidly lethal systemic infection characterized by generalized suppression of host immune functions. DNA sequencing studies reveal that MRV and MYX possess homologous gene members of the T6/T8/T9 family originally described in the terminal inverted repeat (TIR) of SFV. We also describe a gene present in both MYX and MRV genomes, but which has apparently evolved in the SFV genome into a fragmented pseudogene that appears to contribute to the aggressive nature of MYX and MRV infections. Translation of this open reading frame, designated MYXOMA SERPIN 1 (SERP1), reveals a protein sequence with highly significant homology to the super-family of serine protease inhibitors (serpins) which also includes a number of other poxviral proteins. In the MYX genome the SERP1 gene lies entirely within the TIR sequences and is thus present as two copies, while in the MRV genome SERP1 is present in the unique sequences adjacent to the TIR boundary and hence is a single copy. The amino acid homology between the putative active site of SERP1 and those of other serpins predicts that the target enzyme will be different from the known catalog of serine antiprotease substrates. Deletion of this gene from MRV significantly attenuates the disease spectrum induced by the normally lethal virus. Although the MRV-S1 deletion construct (MRV with SERP1 gene deleted) grows in all tissue culture cells tested in a fashion identical to the MRV parent, the majority of rabbits infected with MRV-S1 are able to mount an effective immune response and totally recover from the virus infection to become resistant to subsequent challenge by MRV or MYX.

Amino Acid Sequence↗
PubMed1993

Atypia in breast fine-needle aspiration smears correlates poorly with the presence of a prognostically significant proliferative lesion of ductal epithelium.

Proliferative lesions of breast duct epithelium are associated with an increased risk of subsequent carcinoma. Fine-needle aspiration criteria for these lesions are poorly defined; most studies are retrospective and do not clearly use the classification of Page and Rogers. Suggested criteria for "atypia" include crowded, enlarged, overlapping nuclei in three-dimensional groups or sheets, loss of cohesion, occasional single cells, a homogeneous cell population, chromatin changes, and increased cellularity in older patients. Our prospective series of 1,925 aspirations included 717 breast cases, of which 25 (3.5%) were considered sufficiently atypical to possibly represent proliferative lesions, but were not suspicious for carcinoma. Fifteen patients with histologic follow-up formed the basis for this study. All had physical examinations and mammogram results consistent with fibrocystic change. Their ages ranged from 30 to 70 years (median age, 44 years). Cytologic changes of atypia were cataloged. Histologically, six cases (40%) showed prognostically significant lesions (moderate, florid, or atypical hyperplasia and one lobular carcinoma in situ). Many (60%) cytologically provocative lesions may originate in prognostically trivial lesions. At this time our limited understanding of the cytologic presentation of these lesions indicates that surgical excision is essential in all instances. Efforts to recognize and properly classify these proliferations in cytologic material should continue.

Adolescent↗
PubMed1994

Gastritis: terminology, etiology, and clinicopathological correlations: another biased view.

The histological approach to gastritis, especially the chronic forms, has undergone a series of re-evaluations by different experts over the past decade, mainly because of the recognition of individual disease patterns that have specific clinical and epidemiological implications. The most spectacular of these was the discovery of Helicobacter pylori and its common gastritis, its relation to almost all duodenal peptic ulcers and to most gastric peptic ulcers, its potential as a precursor of first multifocal atrophic gastritis and later tubule-forming gastric carcinomas, and its status as a cause of gastric mucosal lymphomas. During this same decade other classes of gastric reaction and inflammations have been recognized, including chemical injury and lymphocytic gastritis. Also in the same decade the importance of non-steroidal anti-inflammatory drugs (NSAIDs) has emerged as a cause of gastric mucosal injuries. To add emphasis to all these discoveries, biopsies are being performed on stomachs in almost epidemic numbers and each biopsy specimen has the potential of having the features of one or more of these injuries as well as injuries that have yet to be described. To cope with this rapidly expanding gastric inflammatory informational extravaganza, pathologists need some way of dealing with the various entities comfortably and some method of cataloging them in ways that are understandable both to them and to the endoscopists with whom they work. However, if emerging data about the chronic gastritides are correct, it is conceivable that the need to diagnose them, from a strictly clinical standpoint, is limited. Either we may know what is in the biopsy specimen before we see it or what we see may not be important, although it may be intellectually challenging.

Acute Disease↗
PubMed1990

Pitfalls in pediatric urinary sonography.

Our review of pediatric urinary tract ultrasonograms over a period of two and one-half years resulted in a catalog of pitfalls. Cases included normal scans mistaken for abnormal and vice versa. These erroneous diagnoses stemmed from the inappropriate selection of the primary imaging test, improper timing of the ultrasonogram, errors of commission or omission in performance of the scans, and improper interpretation of the findings. For ease of reference, the pitfalls are grouped under bladder, ureters, and kidney with emphasis on the first two which are common sources of error.

Child↗
PubMed1992

Phonological error analysis, development and empirical evaluation.

A method of error analysis, designed to examine phonological and nonphonological reading and spelling processes, was developed from preliminary studies and theoretical background, including a linguistic model and the relationships between articulatory features of phonemes. The usefulness of this method as an assessment tool for phonological ability was tested on a group of normal subjects. The results from the error analysis helped clarify similarities and differences in phonological performance among the subjects and helped delineate differences between phonological performance in spelling (oral and written) and reading within the group of subjects. These results support the usefulness of this method of error analysis in assessing phonological ability. Also, these results support the position that phonological approximation of responses is an important diagnostic feature and merely cataloging errors as phonologically accurate or inaccurate is inadequate for assessing phonological ability.

Child↗
PubMedDate not supplied

Have structural adjustments led to health sector reform in Africa?

This paper explores the issue of whether and how structural adjustment in Sub-Saharan Africa has altered the level and nature of state involvement in the health care system. Stabilization and structural adjustment generally entail a reduction in aggregate demand, especially government spending, and a reduced role for the state in the provision of many goods and services. Consequently, there is an a priori concern that stabilization and adjustment in Africa may have resulted in lower health expenditures with deleterious effects on the health status of the population, particularly the poor. This paper concludes that structural adjustment programs in Africa did not reduce public health expenditures. In fact, many countries experienced higher real expenditures after adjustment. The fact that many indicators of health status deteriorated during the 1980s, however, presents somewhat of a paradox given the patterns of health expenditures. This paradox is resolved, by an investigation of the intrasectoral allocation of health expenditures which reveals that there are systematic biases in public expenditures towards tertiary and curative care, and a general weakness in the public sector's capacity to deliver adequate health care services even with higher real health sector budgets. In many countries, these biases have persisted despite government and donor intentions to promote health care reform. Finally, the paper reviews a set of policy and institutional issues which hinder the efficient use of budget resources, including overcentralization of health care administration, inappropriate drug and supply procurement practices, the lack of mechanisms for cost recovery, and poor organization, financial and personnel management. At each level of analysis, the paper catalogs those instances where progress is being made towards effective health care reform, including intrasectoral budget rationalization, administrative decentralization, the adoption of user fees for cost recovery, privatization in service delivery, particularly through non-governmental organizations, and organizational and management reform.

Africa South of the Sahara↗
PubMed1993

Ivermectin resistance.

In this review of ivermectin resistance, Wesley Shoop discusses the definition of resistance, catalogs all known cases of ivermectin resistance, argues that overmectins and milbemycins belong in the same action family, discusses the possibility of resistance in the filariae, and suggests that detection of ivermectin resistance is the area where future research is most needed.

Journal Article↗
PubMed1992

A clinical trials database as a research tool in health care.

OBJECTIVE: The rapid, efficient, and accurate communication of clinical research findings to both clinicians and researchers is essential to the process of improving medical care. This information should be conveyed in a form that facilitates the interpretation of the complete body of research on a specific condition. Unfortunately, the prevailing system for dissemination of clinical research fails to meet these criteria. This paper proposes a system for cataloging clinical trials and communicating their results in a comprehensive and comprehensible format. METHOD: The system involves the use of a hierarchical matrix structure that allows for the selection and evaluation of related groups of clinical trials. The format of the data is tailored to the requirements of metaanalysis. RESULTS: An example is presented using the treatment of acute Crohn's disease and including a sample metaanalysis of immunosuppressive therapy for this condition. CONCLUSIONS: The hierarchical matrix structure in conjunction with a comprehensive database of clinical trials holds the potential to facilitate access to and interpretation of clinical research.

Acute Disease↗
PubMed1991

Verifying the composition of certain commercial nickel compounds.

Forty commercial samples chosen from three families of nickel compounds were purchased and chemically analyzed. The selection included 21 basic nickel carbonates, 5 nickel sulfides, and 14 nickel oxides sold by 18 producers or distributors in eight countries. The analytical results were compared with the information provided on the container labels. A number of errors were found in the label information ranging from minor inconsistencies and incomplete information to actual misrepresentation of the product. For example, nickel(II) oxides containing only 1-2% Ni(III) are being offered for sale as "nickel(III) oxide, Ni(2)O(3)." Thus researchers should not accept at face value the chemical identity presented by producers or distributors in catalogs and on labels. Since significant variations in biological properties have been found within each of these three families of nickel compounds, researchers should carefully establish which particular member of a family is being studied. Unfortunately, the literature on the biological effects of nickel compounds contains numerous studies where this was not done. Attributing the results of such studies to other or, worse, to all members of the same family of nickel compounds may introduce significant errors into risk assessments.

Drug Labeling↗
PubMed1975

The membrane of giant molluscan neurons: electrophysiologic properties and the origin of the resting potential.

The molluscan neuron, because of its large size and accessibility, has been an important model for studying the electrophysiology of nerve cells. This review catalogs data about specific molluscan neurons, but the greater importance of this material is in the broad picture of how a neuronal membrane maintains internal potential and is responsive to changes in the environment. Electrical properties of the membrane. The mechanisms which contribute to the resting potential in molluscan neurons can be separated into ionic and metabolic components. When the electrogenic sodium pump is eliminated experimentally, the ionic component of the potential follows the constant field equation quite closely. Many of the "constants" and "parameters" which characterize the membrane of molluscan neurons are actually variables which depend upon temperature, ionic environment, and membrane potential. The evaluation of the electrical parameters is complicated by extensive infoldings of the somatic membrane, and by large axons which drain current from the soma. Most molluscan neurons have a very high specific membrane resistance and a correspondingly low potassium permeability. Membrane capacitance is close to the 1 microF/cm2 value which characterizes biological membranes. The current-voltage relation of molluscan neurons may be complicated by inward-going rectification, but if that is inhibited the I-V curve follows the prediction of either the constant field equation or a simple electrical model. Factors which modify membrane behavior. The resting potential of molluscan neurons is very sensitive to changes in temperature and Ko, through a combination of effects upon the electrogenic sodium pump, inward-going rectification, and the membrane "parameters". Inward-going rectification depends upon a rectifying K conductance, and can be eliminated by cold or the removal of Ko. Strong or prolonged currents have time-dependent effects upon the membrane, and excessive polarization leads to a "high conductance state". The underlying (non-rectifying) K permeability of the membrane is relatively insensitive to temperature and ionic changes, whereas the Na permeability increases with warming. Membrane resistance varies with both temperature and ions (because the I-V curve is sensitive to these conditions) but membrane capacitance is relatively insensitive to external factors. Electrogenic sodium transport. Sodium transport is electrogenic in molluscan neurons. It can be stimulated by warm temperatures and an excess of substrate (e.g. high Nai); it can be inhibited by cold, by an absence of substrate (e.g. low Ko), or by pharmacologic agents such as cyanide or ouabain.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗