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Biomedical subjects

C R Taylor

Publications and source records attributed to C R Taylor.

At least 181 records · Page 10Linked to original sources
PubMed1988

Muscle forces during locomotion in kangaroo rats: force platform and tendon buckle measurements compared.

The muscle forces and stresses occurring during normal locomotor activity in kangaroo rats are compared with the peak isometric force developed by the same muscles in situ. Two methods were used simultaneously to determine the stresses (force/cross-sectional area) acting in the ankle extensors during steady-speed hopping and during jumps when animals were startled: a direct measurement using a force buckle surgically implanted around a tendon; and an indirect measurement using a force platform/ciné analysis technique. We obtained essentially the same values with the two techniques. We found that at slow speeds (0.7 m s-1) the ankle extensor muscles of kangaroo rats exerted 20% of the maximum isometric force developed when the muscles were stimulated via the tibial nerve. This increased to 53% at higher speeds (1.9 m s-1). At the animals's preferred hopping speed (1.5 m s-1), peak force was approximately 40% of maximum isometric force. In jumps when animals were startled, peak forces as high as 175% of the maximal elicited isometric force were recorded. These high forces always occurred when the muscles were being stretched. It appears that kangaroo rats utilize nearly the entire range of muscle force possible during normal locomotor events (i.e. up to 175% of maximum isometric force when muscles are stretched).

Animals↗
PubMed1988

Preferred speeds in terrestrial vertebrates: are they equivalent?

Terrestrial animals have 'preferred speeds' within each gait, that are used much more frequently than others for moving along the ground. Energy costs reach minimal values at these speeds within each gait. In this study we asked whether these speeds are mechanically equivalent among different animals (i.e. speeds where the same levels of peak muscle stress occur). If so, this would help in establishing a link between the energetics and the mechanics of the active muscles at these speeds, providing a first step in understanding why energy costs are minimal. We also asked whether peak muscle stress reaches a similar fraction of the maximal isometric stress at these speeds. If so, this would suggest that muscles are structured so that a similar reserve capacity remains, with a similar safety factor for avoidance of injury in response to prolonged repetitive loading. We compared two species that use quite different locomotory methods at their preferred speeds: white rats that gallop and kangaroo rats that hop. We measured peak stress in the ankle extensor muscles of these two species, as they moved at their preferred speeds, using a force platform/ciné analysis technique. We also measured the maximum isometric force that this muscle group could develop in situ in the same individuals. We found the ankle extensors of white rats and kangaroo rats developed virtually identical levels of peak stress at their preferred speeds (70 +/- 6 kPa and 69 +/- 6 kPa, respectively, mean +/- S.E.), despite a fourfold difference in peak ground reaction force per unit body mass exerted on each limb. The values of peak isometric stress in situ were also virtually identical (206 +/- 17 kPa and 200 +/- 9 kPa, respectively). Our finding that the peak muscle stress is about one-third of maximum isometric stress at the preferred speeds is consistent with the idea that these are mechanically equivalent speeds, where the same fraction of available muscle fibres is recruited. Finding nearly identical values in two species that move in such different ways (galloping vs hopping), and have such large differences in ground reaction force exerted by each limb, suggests this may be true more generally for terrestrial vertebrates.

Animals↗
PubMed1988

Speed, stride frequency and energy cost per stride: how do they change with body size and gait?

In this study we investigate how speed and stride frequency change with body size. We use this information to define 'equivalent speeds' for animals of different size and to explore the factors underlying the six-fold difference in mass-specific energy cost of locomotion between mouse- and horse-sized animals at these speeds. Speeds and stride frequencies within a trot and a gallop were measured on a treadmill in 16 species of wild and domestic quadrupeds, ranging in body size from 30 g mice to 200 kg horses. We found that the minimum, preferred and maximum sustained speeds within a trot and a gallop all change in the same rather dramatic manner with body size, differing by nine-fold between mice and horses (i.e. all three speeds scale with about the 0.2 power of body mass). Although the absolute speeds differ greatly, the maximum sustainable speed was about 2.6-fold greater than the minimum within a trot, and 2.1-fold greater within a gallop. The frequencies used to sustain the equivalent speeds (with the exception of the minimum trotting speed) scale with about the same factor, the -0.15 power of body mass. Combining this speed and frequency data with previously published data on the energetic cost of locomotion, we find that the mass-specific energetic cost of locomotion is almost directly proportional to the stride frequency used to sustain a constant speed at all the equivalent speeds within a trot and a gallop, except for the minimum trotting speed (where it changes by a factor of two over the size range of animals studied). Thus the energy cost per kilogram per stride at five of the six equivalent speeds is about the same for all animals, independent of body size, but increases with speed: 5.0 J kg-1 stride-1 at the preferred trotting speed; 5.3 J kg-1 stride-1 at the trot-gallop transition speed; 7.5 J kg-1 stride-1 at the preferred galloping speed; and 9.4 J kg-1 stride-1 at the maximum sustained galloping speed. The cost of locomotion is determined primarily by the cost of activating muscles and of generating a unit of force for a unit of time. Our data show that both these costs increase directly with the stride frequency used at equivalent speeds by different-sized animals. The increase in cost per stride with muscles (necessitating higher muscle forces for the same ground reaction force) as stride length increases both in the trot and in the gallop.

Animals↗
PubMed1988

Lymphoid immunohistochemistry of macaque primates.

The immunohistochemical localizations of 53 monoclonal antibodies with specificities expressed in human lymphoid tissue were investigated on lymph node tissues from Macaca mulatta, M. speciosa, and M. fascicularis using immunoperoxidase techniques. Thirty antibodies showed comparative cross-reactivity. The micro-anatomic distribution of these antigens was closely homologous to that observed in man and antigen densities appeared to be similar. A useful monoclonal antibody panel for immunopathological investigations in macaques was, thereby, defined. Of several pan-T antibodies studied, only OKT11(CD2) showed cross-reactivity. A detailed analysis of the immunocyto-architecture of five rhesus lymph nodes was undertaken. Automated flow cytometry of M. mulatta and M. speciosa peripheral blood showed a broadly similar pattern to man.

Animals↗
PubMed1988

Immunohistochemical characterization of two new monoclonal antibodies (LN-4, LN-5) reactive with human macrophage subsets and derived malignancies in B5-fixed, paraffin-embedded tissues.

Two monoclonal antibodies (LN-4, LN-5) reactive to human macrophages in B5 formalin-fixed, paraffin-embedded tissue sections have been produced by using deparaffinized cell extracts of peripheral blood mononuclear cells. Both monoclonal antibodies were initially identified on paraffin-embedded sections of hyperplastic lymph nodes by using the immunoperoxidase staining procedure. Specificity screens on normal human tissues show that LN-4 and LN-5 stain the cytoplasm of macrophages and histiocytes in hematopoietic organs including Kupffer's cells of the liver and Langerhans' cells of the skin. LN-4 also showed strong positivity with acini of the stomach, whereas LN-5 was positive with mantle zone B lymphocytes of the lymph node and spleen, spermatogonia, and chief cells of the stomach. Both antibodies were strongly reactive with cases of true histiocytic lymphoma but, except for infiltrating macrophages, were entirely negative in Hodgkin's disease and non-Hodgkin's lymphomas. In all cases of nodular sclerosis Hodgkin's disease, LN-4 was positive in macrophagelike cells present in the collagen bands surrounding the Hodgkin's lesions. Both monoclonal antibodies were also positive in macrophages and histiocytes present in a variety of benign lymphoid lesions including persistent generalized lymphadenopathy, Gaucher's disease, sinus histiocytosis, and dermatopathic lymphadenopathy. Because of their specificity for human macrophages, and their ability to stain B5-fixed, paraffin-embedded tissues, LN-4 and LN-5 are important new reagents for the diagnosis and classification of malignant and benign histiocytic lesions.

Animals↗
PubMed1987

Small noncleaved follicular center cell lymphoma: Burkitt's and non-Burkitt's variants in the US. II. Pathologic and immunologic features.

The morphologic criteria for the two variants of small noncleaved follicular center cell (SNC FCC) lymphoma in the Lukes-Collins classification, Burkitt's (BL) and non-Burkitt's variants (NBL), were evaluated and related to the results of multiparameter laboratory and clinical studies. Forty-two patients were studied: 25 cases were classified as BL according to World Health Organization (WHO) criteria. Seventeen cases were classified as NBL on the basis of greater variability in nuclear size and shape, more prominent nucleoli, and greater variation in the amount of cytoplasm. Neoplastic follicles were present in three cases of BL and two of NBL, indicating an FCC origin for this lymphoma. Electron microscopic examination confirmed the light microscopic features. Immunoglobulin (Ig) monoclonality, as demonstrated by immunofluorescence (surface Ig) and/or immunoperoxidase staining for cytoplasmic immunoglobulin (CIg), was demonstrated in 21 of 24 (87.5%) of BL and 13 of 16 (71%) of NBL. Clinically, BL presented more frequently in extranodal sites and with gastrointestinal involvement than NBL. Bone marrow involvement was more common in NBL patients. Both groups had advanced stage disease at diagnosis. The median survival was 10.5 months in BL and 7.7 months in NBL. The results of this study indicate that BL and NBL are biologically related variants of SNC FCC lymphoma but have different presentations, which may be clinically significant.

Adolescent↗
PubMed1987

Two new monoclonal antibodies, Lym-1 and Lym-2, reactive with human B-lymphocytes and derived tumors, with immunodiagnostic and immunotherapeutic potential.

Two new monoclonal antibodies (Lym-1 and Lym-2), reactive with the cell surface of B-lymphocytes and derived tumors, have been produced using tumor cell nuclei preparations as immunogens. Specificity screens using live cell radioimmunoassay techniques with 52 well-characterized human lymphoma and leukemia cell lines showed that both Lym-1 and Lym-2 bound to cell lines of B-cell lineage but were unreactive with those of T-cell, myeloid, or erythroid derivation. The B-cell specificity of these reagents was confirmed on 36 lymphoma and 15 leukemia biopsy specimens by using immunoperoxidase or immunofluorescence techniques. Additionally, flow cytometric analysis of 22 lymphoma biopsies showed that the majority of B-cell tumors were Lym-1 and/or Lym-2 positive and that within a given biopsy, a high percentage of the malignant cell population was stained. In both the immunoperoxidase and flow cytometric studies, reactive T-cells or T-cell lymphomas were consistently negative with the exception of Hodgkin's disease tissues which, in some instances, showed a higher than expected positivity with Lym-1 and Lym-2. Approximately 40% of B-cell chronic lymphocytic leukemias were found to be positive with Lym-1 while 80% were positive with Lym-2. Immunoperoxidase staining of frozen sections of human lymphoid tissues showed that both Lym-1 and Lym-2 stained germinal center and mantle zone B-lymphocytes as well as interfollicular histiocytes. Flow cytometric analysis of normal peripheral blood demonstrated specific staining of B-cells which comprised approximately 8% of circulating lymphocytes. Immunoperoxidase staining of nonlymphoid human organs and tissues revealed weak reactivity of Lym-1 with surface colonic epithelium only. Consistent with these findings, 35 solid tumor cell lines of diverse nature were found unreactive with both Lym-1 and Lym-2. Although standard techniques have thus far failed to identify the antigen recognized by Lym-2, the membrane antigen which binds Lym-1 has been shown by immunoprecipitation and competitive radioimmunoassay studies to be a polymorphic variant of the HLA-Dr antigen. Solid-phase radioimmunoassay techniques have shown that the antigens recognized by Lym-1 and Lym-2 are not significantly modulated after antibody exposure nor shed into the circulation of lymphoma patients. Finally, using iodine-125 labeled preparations of purified Lym-1 and Lym-2, we have determined that both reagents have a relatively large number of antibody binding sites per tumor cell and increased avidity for lymphoma cells when compared to normal and reactive lymph node B-cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Antibodies, Monoclonal↗
PubMed1987

Papillomavirus antigens in anorectal condyloma and carcinoma in homosexual men.

Squamous cell carcinoma of the cervix and vulva has been associated with infection by human papillomavirus. Recent epidemiologic studies have observed more anal carcinoma among single than married men. To investigate this association between human papillomavirus and squamous proliferative lesions of the anus, we studied eight homosexual or bisexual men with recent diagnoses of anorectal carcinoma and six older patients of unknown sexual orientation with similar diagnoses 20 to 30 years ago. Using an immunohistochemical stain for papillomavirus, we found evidence of its presence in the carcinomas of five (63%) of the eight homosexual men and in two (33%) of the six older patients. Only one homosexual patient had the acquired immunodeficiency syndrome. In the possibly immunocompromised patient, human papillomavirus antigen is present in anorectal dysplasia and carcinoma.

Adult↗
PubMed1987

A multicenter, randomized, placebo-controlled trial of a new form of intravenous recombinant tissue-type plasminogen activator (activase) in acute myocardial infarction.

A new, predominantly single chain preparation of recombinant tissue-type plasminogen activator was evaluated to determine coronary thrombolytic efficacy in 100 patients with acute myocardial infarction. At 3.6 +/- 1.2 hours (mean +/- SD) from symptom onset, patients received either intravenous tissue plasminogen activator (1.25 mg/kg body weight over 3 hours) or placebo on a 3:1 randomized, double-blind basis. Coronary angiography, performed 68 +/- 13 minutes after initiation of the study drug infusion, demonstrated patency of the infarct-related artery in 40 (57%) of 70 patients in the tissue plasminogen activator group compared with 3 (13%) of 23 patients in the placebo group (p less than 0.001). Patients in the placebo group were then eligible to receive intracoronary streptokinase. At 90 minutes the patency was observed in 49 (69%) of 71 tissue plasminogen activator patients compared with 5 (24%) of 21 placebo patients (p less than 0.001). At 120 minutes patency was observed in 59 (79%) of 75 patients of the tissue plasminogen activator group and in 10 (40%) of 25 in the intracoronary streptokinase/placebo group. A nadir value of less than 100 mg/dl fibrinogen occurred in 8 (11%) of 73 patients receiving tissue plasminogen activator versus 8 (40%) of 20 patients treated with intracoronary streptokinase (p = 0.002). Moderate or severe bleeding episodes occurred in 39% of patients treated with tissue plasminogen activator compared with 32% of patients who received placebo/intracoronary streptokinase (p = NS). Thus, this tissue plasminogen activator preparation achieves a high rate of recanalization and, at the doses employed, exhibits increased fibrinogen sparing compared with intracoronary streptokinase.

Angiography↗
PubMed1987

Immunohistology of persistent generalized lymphadenopathy. Evidence for progressive lymph node abnormalities in some patients.

Immunohistologic analysis of cellular changes in serial lymph node biopsies of eight patients with persistent generalized lymphadenopathy (PGL) syndrome was performed and correlated with clinical and laboratory findings to better determine the natural history of human immunodeficiency virus (HIV) infection. The authors observed decreased follicle size and area in the second biopsies of six of the eight patients, associated in some with increased numbers of B-cells in medullary regions (four of eight) and more involuted follicles (four of eight). Five cases showed progressively increased paracortical areas in the second biopsies, with increased numbers of T-cytotoxic/suppressor cells and decreased T-helper cells. Seven of the patients also had a progressive loss of T-helper cells in the peripheral blood. These findings provide tissue and peripheral blood evidence for progressive immunologic deterioration in some patients with PGL.

AIDS-Related Complex↗
PubMed1987

Proton relaxation times in bleomycin-induced lung injury.

Pulmonary fibrosis and inflammation induced in mice by biweekly injection of low doses (20 mg/kg) of bleomycin chronically administered subcutaneously was associated with a significant increase in T2 values measured in vitro (54.6 +/- 20.7 ms vs. 36.2 +/- 3.8 ms in controls). T1 values, however, were not altered significantly (613 +/- 124.6 ms vs. 666 +/- 105.7 ms in controls). Lung water content did not change (79.1 +/- 2.5% vs. 78.4 +/- 0.98% in controls, NS). Water content to dry weight ratio in the control group (3.63 +/- 0.212) did not differ significantly from that in the experimental group clinically treated with bleomycin (3.84 +/- .618). However, morphometric and histologic analysis indicated that in 71% of the chronically treated mice, there was marked pulmonary fibrosis (mean area of involvement 3.5 +/- 8.1% vs. 0.25 +/- 0.15% in controls, P less than .01). In addition, there was marked increase in pulmonary cellularity and infiltration by lymphocytes and macrophages (mean area of macrophage infiltration 8.71 +/- 13.256% vs. 1.17 +/- 1.404% in controls). The alteration in T2 in bleomycin damaged lung occurred in the absence of change in overall water content. However, the change in cellularity indicates an alteration of water distribution between the cellular, intravascular, and interstitial components induced by the measurable fibrotic and inflammatory response to bleomycin.

Animals↗
PubMed1987

Focal liver masses: differential diagnosis with pulsed Doppler US.

Duplex Doppler ultrasound (US) was used in 68 consecutive patients with focal liver lesions, including 12 hepatocellular carcinomas, one cholangiocarcinoma, 37 metastases, 15 hemangiomas, one hemangioendothelioma, and two focal nodular hyperplasias. Of the hepatocellular carcinomas, six were diffusely hyperechoic, two were hypoechoic, two were single hyperechoic lesions, and two were multifocal and hyperechoic. All ten tumors with Doppler shifts of 5 kHz or above proved to be hepatocellular carcinomas. The other two hepatocellular carcinomas showed Doppler shifts of 3 kHz. In contrast, no hemangioma showed shifts above 0.7 kHz, and ten of the 15 gave no detectable signal. Of the metastases, 20 gave no signal and 17 had signals of up to 4 kHz. Three-kilohertz signals were also obtained from a cholangiocarcinoma, a hemangioendothelioma, and focal nodular hyperplasia. Correlation with angiographic findings suggested that the high-velocity Doppler signals were associated with large pressure gradients due to arteriovenous shunting. Duplex Doppler US can therefore aid in the differential diagnosis of diffuse and focal liver lesions.

Aged↗
PubMed1987

Substrate and O2 fluxes during rest and exercise in a high-altitude-adapted animal, the llama.

Llamas were trained to exercise on a treadmill at graded speeds. O2 uptake values at rest, at modest exercise (ME, 0.58 m/s), and at heavy exercise (HE, 1.84 m/s) were 0.069, 0.297, and 0.594 ml O2 X kg-1 X s-1. Corresponding values for cardiac output were 1.64, 4.39, and 6.85 ml X kg-1 X s-1. Palmitate, glucose, and lactate replacement rates (Ra values) were determined at these varying work rates using a single-bolus injection of 14C- or 3H-labeled metabolites, two at a time. Ra values for palmitate, glucose, and lactate at rest were 6.2, 61.4, and 36.1 mumol X kg-1 X min-1, respectively. During ME, the Ra values for glucose and palmitate increased about twofold but showed no further increase when exercise intensity was increased about twofold. In contrast to these results, Ra values for lactate increased much more with increasing work rate. A combination of increased perfusion (increased cardiac output) and increased lactate availability (increased plasma concentration) could account for the lactate Ra data. During prolonged ME, the Ra for lactate decreased because lactate availability decreased; concurrently, both the plasma free fatty acid availability and the Ra values for palmitate greatly increased. Because O2 carrying capacity is low in the llama (as in all high-altitude-adapted mammals), a given level of exercise required exaggerated increases in cardiac output (and hence in perfusion rates of working muscles). As a result, the flux rates of palmitate, glucose, and lactate through the plasma compartment could readily account for O2 flux rates even at relatively high sustainable rates of exercise.

Acclimatization↗
PubMed1987

Patterns of fibrin deposits in carotid artery plaques.

We evaluated 40 consecutive carotid endarterectomy specimens for the presence of fibrin. Intraplaque hemorrhage was noted in 93% of specimens. At the plaque surface, there were two patterns of fibrin distribution. Type I, suggesting a lumen thrombus, was found in 7 specimens. Type II, suggesting an intraplaque hemorrhage at the lumen surface, was found in 15 specimens. These changes were not significantly associated with the presence of ischemic symptoms or the use of antiplatelet or anticoagulant medications. All specimens with Type I change had arteriographic evidence of at least 70% diameter stenosis. The frequent lack of fibrin at the plaque surface suggests that there may be inherent limitations of standard medical treatment for carotid artery disease.

Arteriosclerosis↗