Biomedical subjects
Publications and source records attributed to M Tucker.
A group of anovulatory women have been identified as being particularly difficult to treat with pulsatile luteinising hormone releasing hormone (LHRH). Further investigation shows that sub-division into two groups is possible on the basis of ovarian morphology on ultrasound imaging. Ovulation can be successfully induced in women with megalocystic ovaries and 14 of those women treated conceived.
Spleen cells recovered from mice during a primary infection with Ross River virus showed a virus-specific proliferative response when challenged in vitro. The majority of the proliferating cells were T-lymphocytes. In contrast, there was little detectable migration inhibition factor production by these spleen cells and little or no virus-specific cytotoxic activity. Sub-cutaneous challenge with virus elicited a weak delayed type hypersensitivity reaction.
Sarcolemmal perforations can be produced in bundles of rat right ventricular cells by either perfusion of the heart or soaking of the bundles with a solution containing 10 mM EGTA. All cells are affected and lose approximately 40% of the surface membrane. In these cells it is possible to show cAMP regulation of contractility (maximum Ca-activated force) without cAMP regulation of Ca sensitivity (pCa for 50% of maximum Ca-activated force). Therefore, the target molecule for cAMP is different for the two regulatory systems. Both regulatory systems can be slowly washed out of the cell by 10 mM EGTA solution but not by relaxing or contraction solutions. A model for regulation of Ca sensitivity is proposed.
Hyperpermeable cells from rat heart contain a cAMP-dependent system that can increase the maximum Ca-activated force (contractility) of the contractile proteins. In two different conditions where the relative concentration of the myosin isozymes changes, i.e., hypothyroidism and aging, the size of the increase in contractility from activation of the cAMP-regulated system varies closely with the relative concentration of V1, the isozyme of myosin with the greatest Ca- and actin-activated ATPase activity. The existence of another system for the regulation of the slow isozyme V3 has been demonstrated, and it may be inhibited by beta-adrenergic activity. The possibility of cAMP-dependent myosin regulation of contraction in addition to Ca regulation of troponin is considered. Phosphorylation of the contractile proteins themselves is not required for the increased contractility.
Several of the contractile proteins of the heart can be phosphorylated, but in studies with isolated proteins only phosphorylation of the inhibitory subunit of troponin (TnI) produces a major change in the properties of the contractile system. As TnI is phosphorylated, the concentration of calcium required for activation of contraction is increased. Phosphorylation of the tropomyosin-binding subunit of troponin (TnT) or of the light chain of myosin fails to change ATPase activity of the isolated protein system. Phosphorylation of TnI is stimulated by the beta-adrenergic system and inhibited by the cholinergic system. Maximum calcium-activated force produced by the contractile system can be increased in hyperpermeable cardiac cells by cyclic AmP (cAMP) or agents that stimulate cAMP synthesis. This change in the contractile system, which appears to be part of the physiological response to beta-adrenergic stimulation, is mediated by phosphorylation of an intermediate that then modifies the contractile system. Phosphorylation of the contractile proteins is not involved.
Human red blood cell ghosts, prepared by simple hypotonic lysis are filled with cytoplasmic proteins. These solid ghosts can transport K+ and Na+ against concentration gradients in the presence of ATP. In hollow red cell ghosts prepared by repeated hypotonic lysis followed by high salt wash, this ability to transport K+ and Na+ in the presence of ATP is lost even though these hollow ghost membranes remain intact and are equipped with Na+-K+ activated ATPase.
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The plasma concentrations of the complement components C3 and C4, as well as the split products C3c and C3d, were measured before, during, and after normal pregnancy. Significantly increased values were observed in the C3 and C3d levels in the second and third trimesters of pregnancy. The level of C4 was not significantly affected by pregnancy and C3c could not be detected using electroimmunoassays. These results suggest that the increased C3 split-product levels observed reflected an increased turnover of native C3 rather than activation of the complement cascade.
A histochemical method for distinguishing isozymes of myosin in rat ventricles has been developed. The procedure involves preincubation in pH 10.5, which inhibits Ca-activated ATPase of the V3 isozyme but not the V1 isozyme of myosin. The specificity of the technique has been demonstrated by comparison of results in hearts from young euthyroid and hypothyroid rats, in which the predominant isozymes are, respectively, V1 and V3. The technique is capable of detecting as small a change in the relative amount of V1 as 15% of the total myosin. Isoenzymes appear to be uniformly distributed within each ventricular cell. There is only a small difference in the content of V1 among the cells in a ventricular chamber of hearts from young euthyroid and hypothyroid rats, but in the period of rapid transition of isozyme content after thyroidectomy, there is considerable heterogeneity of V1 concentration among the cells. The functional implications of the mixture of isozymes is discussed.
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In a study of epidemic polyarthritis in central and northern Queensland, clinical disease was observed most frequently in urban-dwelling adult females. Clinical and subclinical infections were detected year round, although the majority of clinical infections occurred between the months of January and June. In the communities studied, there were approximately 50 subclinical infections for each clinical infection. There was no detectable association between any HLA-A or HLA-B phenotypes and epidemic polyarthritis.
Immunoglobulin M antibody to Ross River virus was found in the cord blood of 11 368 children born to mothers who were pregnant during the epidemic of Ross River virus infection in Fiji, in 1979. Since IgM antibody does not normally cross the human placenta, these findings are suggestive of in-utero infection. Antibody to Ross River virus was also present in eight of the 11 mothers of children with IgM-positive cord blood. One of the mothers with IgM-negative blood had no detectable haemagglutination-inhibiting antibody to Ross River virus. All children appeared normal at birth.
Infection of pregnant mice with Ross River or Getah viruses after the establishment of a functional placenta resulted in fetal infection with these viruses. However, only with Ross River virus was there any significant fetal death. There was significant post-partum mortality in mice infected in utero with Ross River but not with Getah virus. In contrast, significant post-partum mortality occurred in Murray Valley encephalitis virus-infected mice despite the inability of the virus to cross the placenta. Infection of mice with Ross River, Getah, or Murray Valley encephalitis viruses before placentation had occurred (5th day post-conception) did not result in fetal infection although there was significant post-partum death in litters born to Ross River virus-infected mothers.
By studying nuclear magnetic resonance water proton spin-lattice relaxation times (T1 and T2) of normal mouse and rat tissues at varying water contents and by comparing the data with those obtained from five types of cancer cells in ascites form, we concluded that differences in total water contents between normal tissues and cancer cells contribute less than 10% to the differences between the longer T1 of cancer cells as compared to the T1 of normal tissues. In spite of the diverse origin of the five types of cancer cells studied, their T1 and T2 as well as water contents were confined within relatively narrow limits. We suggested that all 5 ascites tumors studied are maximally deviated and that the physical state of the water in all maximally deviated cancer cells is very similar.
To compare the effectiveness of manual and mechanical chest compression during cardiopulmonary resuscitation, 50 patients who suffered cardiac arrest were randomly allocated to receive manual or mechanical chest compression. Randomization was performed after failure of initial resuscitative measures but within ten minutes after the onset of cardiac arrest (mean, 6.4 +/- 1.2 min). Ten patients from each group survived longer than one hour following resuscitation. Three from the mechanical group and two from the manual group were eventually able to leave the hospital. Thus mechanical compression appears comparable with manual compression when manual compression is performed under ideal conditions. Mechanical chest compression may be employed when trained personnel are not readily available or where manual compression is technically difficult to perform.
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Explore the source record for details and available documents.