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Biomedical subjects

C A Phillips

Publications and source records attributed to C A Phillips.

At least 109 records · Page 6Linked to original sources
PubMed1981

Muscle fiber recruitment and blood pressure response to isometric exercise.

Blood pressure was recorded during fatiguing and nonfatiguing isometric contractions of a slow-twitch muscle (the soleus) and a mixed muscle (the medial gastrocnemius) of the cat. Four tensions were examined in each muscle; 10, 25, 40, and 70% of the muscle's initial strength (tetanic tension of the unfatigued muscle). All experiments were also repeated at two muscle temperatures, 28 and 38 degrees C. For the soleus muscle, there was no change in the blood pressure during isometric contractions. For the medial gastrocnemius muscle, both the systolic and diastolic blood pressure increased markedly when either all or just the fast-twitch motor units were stimulated; however, when only the slow-twitch motor units were stimulated, a lower pressor response was observed. Venous blood samples were drawn before, during, and after fatiguing and nonfatiguing contractions of both muscles to determine the K+ concentration in the venous blood. The mean increase in the K+ concentration during contractions was 0.6 meq/l for the slow-twitch motor units of the soleus and 5.1 meq/l for the motor units in the medial gastrocnemius.

Animals↗
PubMed1981

Blood flow and metabolism during isometric contractions in cat skeletal muscle.

The muscle blood flow, oxygen uptake, carbon dioxide production, muscle and blood lactate, muscle ATP, creatinine phosphate, glycogen, and venous pH were measured in the soleus (a slow-twitch muscle) and the medial gastrocnemius (a fast-twitch muscle) of the cat during fatiguing isometric exercise. Five tensions were examined: 10, 25, 50, 75, and 100% of the initial strength of the muscles (tetanic tension of the unfatigued muscle). Contractions were either sustained to fatigue or, for tensions of 10 and 25% initial strength of the soleus muscle, were sustained for 3 min. Analysis of the blood flow and metabolites from these muscles showed that the soleus was heavily dependent on its blood supply, using aerobic metabolism as the predominant pathway, whereas the medial gastrocnemius muscle seemed to use anaerobic metabolism even at low isometric tensions.

Adenosine Triphosphate↗
PubMed1981

Studies on the involvement of prostaglandins in implantation in the rat.

Studies of prostaglandin (PG) production by uterine homogenates of rats in early pseudopregnancy and pregnancy showed that production of 6-oxo-PGF-1 alpha, PGF-2 alpha and PGE-2 peaked on Day 5 of pseudopregnancy whereas only 6-oxo-PGF-1 alpha and PGE-2 peaked on Day 5 of pregnancy, the day of implantation. 6-Oxo-PGF-1 alpha was the major product in both reproductive states. Indomethacin treatment of rats during early pregnancy caused a delay in implantation, a significant reduction in uterine weight, and a much reduced number or absence of implanted blastocysts in the uterus on Day 9. Plasma progesterone levels were also significantly lower in indomethacin-treated, pregnant rats. These findings support roles for prostaglandins in implantation, and in fetal development.

6-Ketoprostaglandin F1 alpha↗
PubMed1981

Induction in C57BL/KsJ mice of complement-dependent antibody cytotoxic to cultured beta cells.

Despite widespread evidence that autoimmune mechanisms may contribute to the beta cell necrosis associated with type I insulin-dependent diabetes mellitus (IDDM), it has not heretofore been demonstrated that islet cell antibodies (ICAs), directed primarily against cytoplasmic antigens, are capable of specific lysis of beta cells. We utilized a readily accessible source of mouse pancreatic islets [CBA/J mice lacking exocrine pancreas (exocrine pancreatic insufficiency syndrome)] to experimentally induce ICAs inbred mice. Homogenates of these islets were injected weekly for four weeks into syngeneic (CBA/J) and allogeneic (A/J, C57BL/6J, C57BL/KsJ) recipients. Only C57BL/KsJ inbred mice showed the induction of a high titer (greater than or equal to 160) antiserum cytotoxic to 51Cr-labeled CBA/J lymph node target cells. Neither the immunized C57BL/sJ mice with circulating ICAs nor any of the other immunized strains showed any decrease in glucose tolerance as compared with vehicle controls. Moreover, no morphologic evidence of islet necrosis or atrophy was apparent. Thus the ICAs induced were reactive with alloantigenic determinants of the donor and unreactive with antigenic determinants of the recipient strain. The C57BL/KsJ antiserum was further screened for anti-islet cell cytotoxic activity using both a 51Cr release assay from CBA/J islet cell monolayer cultures, and immunocytochemical staining of sections of Bouin's fixed, paraffin-embedded pancreas. This antiserum was cytotoxic to CBA/J beta cells in monolayer culture, but not the other non-beta islet cell types. Immune lysis of the beta cell required rabbit complement. At a concentration of 1% antiserum and 4% complement, beta cell lysis was evident between 3 and 4 h at 37 degrees C. Ultrastructural examination of beta cells exhibiting cytopathic changes revealed cytoplasmic disarray rather than any obvious lytic events at the plasma membrane. Grossly distended, rough, endoplasmic reticulum containing intracisternal type A retrovirus was the most prominent feature distinguishing antiserum and control serum-treated beta cells. This model system suggests that ICAs which recognize beta cell cytoplasmic antigens are capable of specifically lysing beta cells via a complement-dependent mechanism. Immunocytochemical staining revealed that, in addition to islet beta-cells,, the antiserum (1/500 dilution) stained a macrophage-like cell in the spleen and lymph nodes, as well as an epithelial-like cell in the thymus. The possibility is discussed that this multiple specificity may have been due to passenger leukocytes present in the islet homogenates used to immunize.

Animals↗
PubMed1981

The influence of fiber composition, recruitment order and muscle temperature on the pressor response to isometric contractions in skeletal muscle of the cat.

The blood pressure response to isometric exercise was examined in the medial gastrocnemius muscle of the cat at muscle temperatures of 28 and 38 degrees C. Contractions were sustained at tensions of between 10 and 100% of the muscle's initial strength (tetanic tension of the unfatigued muscle) with recruitment proceeding from either the fastest to the slowest or from the slowest to the fastest motor units, respectively. The results of these experiments showed that the blood pressure response throughout the duration of contractions at tensions greater than 10% of the initial strength was constant by either order of recruitment and for both muscle temperatures examined, the mean blood pressure rising linearly from an average value of 101.2 +/- 10.3 mm Hg at the onset of the contraction to 146.3 +/- 14.2 mm Hg at the point of fatigue. In contrast, during contractions at 10% of the initial strength at both muscle temperatures, the blood pressure was lower during the first 20% of the contractions when recruitment proceeded from the slowest to the fastest motor units but stayed the same throughout the remainder of the contractions. The results of these experiments indicate the importance of muscle fiber composition in determining the blood pressure response for weak isometric contractions.

Animals↗
PubMed1980

Suppression by progesterone of nonspecific in vitro lymphocyte stimulation in mice as a mechanism for the enhancement of herpes simplex virus type 2 vaginal infection.

The role of antibody, interferon, and cell-mediated immunity (CMI) were studied to determine the mechanisms for progesterone enhancement of vaginal herpes simplex virus type 2 (HSV 2) infection in mice. Three groups of mice were studied: nonpregnant control, pregnant, and nonpregnant progesterone-treated mice. Vaginal infection with HSV 2 did not elicit a neutralizing antibody or a systemic interferon response in any of the groups tested. Splenic lymphocytes from noninfected and infected mice were stimulated in vitro with a nonspecific T-cell mitogen concanavalin (Con A) to measure the proliferative phase of CMI in these groups of mice. No suppression of (3H) thymidine (3HTdR) uptake was found in the pregnant or nonpregnant, progesterone-treated animals as compared to nonpregnant control mice. When progesterone was added directly to the splenic lymphocytes and continuously present during Con A stimulation a statistically significant depression of 3HTdR incorporation was found. We concluded that progesterone depresses Con A stimulation of murine lymphocytes, but progesterone must be continuously present to do so.

Animals↗
PubMed1980

Mechanical and electrical correlates of isometric muscle fatigue in skeletal muscle in the cat.

The amplitude and duration of motor unit action potentials, the rise time, peak tension, and half relaxation time of an isometric twitch, the force-velocity relationship, and tetanic tension were measured at the beginning (fresh muscle) and at the end of a fatiguing isometric contraction at a tension of either 40 or 70% of the initial strength in the soleus (a slow twitch muscle) and the medial gastrocnemius (a fast twitch muscle) of the cat. These same parameters were also measured at set intervals following these contractions to assess their rate of recovery to pre-exercise values. At The end of a fatiguing contraction at either tension examined, Vmx, twitch tension and tetanic tension, were all reduced while there was a prolonged twitch duration and duration of the motor unit action potential for both types of muscle. The height of the motor unit action potential was only marginally effected by muscle fatigue. Following the fatiguing contraction, the endurance required several hours to recover in the medial gastrocnemius muscle but recovered fully within 15 min after either tension in the soleus muscle. Tetanic tension and twitch tension both required less than 10 min for full recovery in the medial gastrocnemius muscle but recovered fully to the pre-exercise values within 3 min following fatiguing isometric contractions in the soleus muscles. Vmx, and the height and duration of the motor unit action potential both recovered within 1 min following the end of the exercise.

Animals↗
PubMed1980

Arthroplasty of the rheumatoid wrist with silicone rubber: an early evaluation.

A review of the results of 37 arthroplasties of the wrist with flexible silicone, done at least 6 months before, in patients with rheumatoid arthritis showed six (16%) to have residual discomfort and two (5%) to have recurrent deformity. Pain was the primary indication for treatment in 31 and deformity in six. Three of 37 wrists had prosthetic fractures (8%). Ten patients who had the opposite wrist fused before the arthroplasty felt the movable wrist was more functional. Contraindications are marked deformity, significant instability, excessive bone loss, and multiple tendon ruptures.

Adult↗
PubMed1980

Enteroviruses in Vermont, 1969-1978: an important cause of illness throughout the year.

Enteroviruses continue to play an important role in both epidemic and sporadic febrile diseases. Of the clinical specimens submitted for diagnosis during a 10-year period (1969-1978) at the Medical Center of Vermont Hospital, Burlington, a wide variety of diseases were associated with the isolation of enteroviruses. Among these diseases were aseptic meningitis, hand-foot-and-mouth disease, diarrhea, pleurodynia, myocarditis, herpangia, and fevers. In 1972 a single enterovirus serotype, coxsackievirus B5, WAS SOLELY RESPONSIBLE FOR EPIDEMIC DISEASE. During the other nine years of the study, a variety of enteroviruses were isolated during epidemics. Although epidemics were always seen during the summer and early fall, enteroviruses which may cause sporadic disease were isolated in each of the 12 months. An awareness by both practicing physicians and health officers not only of the epidemic potential of enteroviruses in summer and fall but also throughout the year will aid in the diagnosis and therapy of these illnesses.

Adolescent↗
PubMed1980

Maternal and neonatal infection with coxsackievirus.

Evidence is growing that relates maternal coxsackievirus infection to increased neonatal mortality and an increase of congenital anomalies. Four cases of fulminant perinatal coxsackievirus infections that were fatal to the newborns are presented. Coxsackievirus infections in pregnancy are usually either subclinical or produce minimal symptoms in the mother. The cases presented point out the potential severity of coxsackievirus infections in the neonatal period. Prevention of the disease and isolation of infected individuals are the mainstays of therapy.

Adolescent↗
PubMed1980

The effect of elbow angle on the isometric strength and endurance of the elbow flexors in men and women.

Ten male and ten female volunteers served as subjects in these experiments to determine the effect of elbow angle on isometric strength of the biceps muscles and on the ability to sustain an isometric tension to fatigue (endurance). As reported by others, we found that for each individual, there existed one elbow angle at which he or she could exert his greatest isometric strength. When maintaining an absolute work load to fatigue, exercise at this angle resulted in the longest endurance; in contrast, endurance was the same at any work load relative to the maximum strength for a given elbow angle.

Adult↗