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Biomedical subjects

K Farmer

Publications and source records attributed to K Farmer.

At least 19 recordsLinked to original sources
PubMed1992

Alternative multimeric structures affect myogenin DNA binding activity.

The native molecular weight of the basic helix-loop-helix (bHLH) proteins myogenin, MyoD, and E12 was calculated from their mobilities on sucrose gradients and molecular sieve chromatography. The muscle bHLH proteins associate to form a variety of higher order complexes, most of which are larger than dimers. Homodimers bind to DNA sequences such as the MEF-1 site in the creatine kinase enhancer whereas homotetramers and larger forms do not recognize this DNA sequence. The ubiquitous bHLH protein E12 forms monomers or homodimers with little evidence for higher order complexes. Mixtures of myogenin and E12 show some heterodimeric structures, but most of the myogenin remains in large complexes. This result using purified proteins is also obtained in nuclear extracts from differentiated myotubes, in which most of the myogenin is present in large complexes that do not bind to the creatine kinase enhancer. A fusion protein containing only the myogenin HLH region forms large homomeric complexes. A model is presented in which each helix associates with a different subunit to form chains or ring structures to explain these observations. The partition of myogenin in nuclear extracts into dimers that recognize known DNA sequences and higher order complexes that do not raises important new issues concerning the regulation of skeletal muscle bHLH protein activity during myogenesis.

Animals↗
PubMed1992

Preliminary studies on the interaction of TNF alpha and IFN gamma with alpha 2-macroglobulin.

The binding of 125I-labelled recombinant human TNF alpha and IFN gamma to isolated human blood alpha 2-macroglobulin has been investigated using molecular sieving procedures and non-denaturing PA gel electrophoresis in combination with autoradiography. These studies revealed that both cytokines readily bind to the electrophoretically fast form of alpha 2M generated by methylamine or protease treatment of this protein. PAGE/SDS gel investigations indicated that TNF alpha bound non-covalently while the IFN gamma interaction was covalent in nature. Preliminary competition studies also indicate that cold TNF alpha and IL-2 are more effective than cold IFN gamma at inhibiting the binding of labelled IFN gamma to alpha 2M. Bioassays revealed that "native" alpha 2M or its derivatives at 2 mg/ml concentration did not impair the antiproliferative effects of TNF alpha and IFN gamma on susceptible bladder tumour cell lines. Furthermore they did not interfere in the induction of Class II antigen expression by IFN gamma on inducible cell lines or in a 2-site ELISA assay for TNF.

Antigens, Neoplasm↗
PubMed1992

MyoD, myogenin independent differentiation of primordial myoblasts in mouse somites.

The accumulation of two myogenic regulatory proteins, MyoD and myogenin, was investigated by double-immunocytochemistry and correlated with myosin heavy chain expression in different classes of myoblasts in culture and during early myogenesis in vivo. During in vitro differentiation of fetal myoblasts, MyoD-positive cells were detected first, followed by the appearance of cells positive for both MyoD and myogenin and finally by the appearance of differentiated myocytes and myotubes expressing myosin heavy chain (MHC). A similar pattern of expression was observed in cultures of embryonic and satellite cells. In contrast, most myogenic cells isolated from newly formed somites, expressed MHC in the absence of detectable levels of myogenin or MyoD. In vivo, the appearance of both myogenin and MyoD proteins was only detected at 10.5 d postcoitum (d.p.c.), when terminally differentiated muscle cells could already be identified in the myotome. Parasagittal sections of the caudal myotomes of 10.5-d-old embryos showed that expression of contractile proteins preceded the expression of myogenin or MyoD and, when coexpressed, MHC and myogenin did not co-localize within all the cells of the myotome. In the limb bud, however, many myogenin (or MyoD) positive/MHC negative cells could be observed in the proximal region at day 11. During further embryonic development the expression of these proteins remained constant in all the muscle anlagens examined, decreasing to a low level during the late fetal period. Western and Northern analysis confirmed that the myogenin protein could only be detected after 10.5 d.p.c. while the corresponding message was clearly present at 9.5 d.p.c., strongly suggesting a posttranscriptional regulation of myogenin during this stage of embryonic development. These data show that the first myogenic cells which appear in the mouse myotome, and can be cultured from it, accumulate muscle structural proteins in their cytoplasm without expressing detectable levels of myogenin protein (although the message is clearly accumulated). Neither MyoD message or protein are detectable in these cells, which may represent a distinct myogenic population whose role in development remains to be established.

Animals↗
PubMed1992

Multimeric structures influence the binding activity of bHLH muscle regulatory factors.

Sucrose gradients and molecular sieve chromatography were used to determine the native molecular weight of the basic HLH proteins myogenin, MyoD and E12. The muscle bHLH proteins not only formed dimers but also associated in a variety of higher order complexes. Although homodimers bind to DNA sequences such as the MEF-1 site in the creatine kinase enhancer, homotetramers and larger forms do not recognize this DNA sequence. Little evidence for complexes larger than dimers was found for the ubiquitous bHLH protein E12. Most of the myogenin remains in large complexes when myogenin and E12 are mixed. The same result was obtained in nuclear extracts from differentiated myotubes, in which most of the myogenin was found to be present in large complexes that do not bind to the creatine kinase enhancer. A fusion protein that contains only the myogenin HLH region fused to glutathione-S-transferase also forms large homomeric complexes. A model to explain these results is that each helix of the HLH motif can associate with a different subunit to form chains or ring structures. The presence of myogenin in nuclear extracts as both dimers that recognize known DNA sequences as well as higher order complexes that do not raises significant issues concerning the regulation of skeletal muscle bHLH protein activity during myogenesis.

Animals↗
PubMed1989

Morbidity from acquired cytomegalovirus infection in a neonatal intensive care unit.

In a prospective study of transfused neonates, 32 of 262 infants were viruric at greater than 20 days of life. Of 212 neonates whose early status was known, postnatally acquired infection was proven in 21, two of whom were seronegative at birth and were thought to have transfusion-acquired cytomegalovirus (CMV). Maternal transmission of CMV is important in this population as there was 91% seropositivity for CMV at birth among the 21 babies who acquired CMV compared with 55% positivity among 150 babies who did not shed CMV (P less than 0.01). Significantly increased morbidity (increased length of stay in hospital, increased use of antibiotics, and longer duration of antibiotic administration) was found in babies with acquired CMV compared with matched controls who did not become viruric. Significant morbidity and mortality was not restricted to the two seronegative babies with transfusion-acquired CMV. The cost of providing CMV antibody negative blood for this neonatal unit would be less than the cost of providing the extended hospital care needed by the two babies with transfusion-acquired CMV found during this 3 year study.

Cytomegalovirus↗
PubMed1987

A combination of hepatitis B vaccine and immunoglobulin does not protect all infants born to hepatitis B e antigen positive mothers.

In 42 infants of hepatitis B e antigen positive carrier mothers a randomised study of a low dose (5 micrograms) hepatitis B vaccine regimen starting within 24 hours of birth with or without hepatitis B immunoglobulin (0.25 ml/kg) showed that in the vaccine group 72% were antibody positive at the age of one year and in the vaccine plus immunoglobulin group 81%. In the vaccine group four of 18 infants were not protected and in those infants receiving vaccine plus immunoglobulin three of 21 were HBsAg carriers by 12 months of age. Hepatitis B vaccine either with or without concomitant HBIg did not protect all babies born of HBeAg positive mothers, from developing the HBsAg carrier status. Thus for full protection of all infants a more vigorous immunisation programme will be necessary.

Carrier State↗
PubMed1985

Passive immunoprophylaxis of hepatitis B virus infections in newborn infants.

Newborn infants of mothers who were chronic carriers of hepatitis Bs antigen (HBsAg) were randomly allocated to be treated or not treated with hyperimmune hepatitis B immunoglobulin (HBIg) at birth and six weeks and were then followed up to one year with sequential blood tests. Ninety percent of all untreated infants born of mothers positive for both HBsAg and hepatitis Be antigen became chronic carriers of HBsAg at one year. In contrast only 9% of infants treated with HBIg became HBsAg positive. Mothers who were HBsAg positive but hepatitis Be antigen negative only uncommonly infected their infants, with 6% being HBsAg positive at one year. Nearly all infections were in Pacific Islanders, Maoris or Asians. It is recommended that antenatal testing of these groups most at risk for hepatitis B virus spread, be initiated, followed by passive immunoprophylaxis with HBIg of infants born of HBsAg, HBeAg positive mothers.

Carrier State↗
PubMed1978

Escherichia coli meningitis in the newborn: follow-up study.

Followup study of 22 cases of meningitis due to Escherichia coli (E. coli) in the newborn period showed a mortality rate of 7 out of 22 (31.88%), severe physical and mental sequelae occurred in one case and mild to moderate sequelae in two others. Most psychometric tests were within normal range in the survivors examined. There was a correlation between low birth weight and a high CSF protein with adverse prognosis.

Child↗
PubMed1978

Low-temperature pasteurisation of human milk.

Human milk was pasteurised at 62.5 degrees C for 30 minutes. This treatment resulted in a 99.99 percent drop in the bacterial count of the milk. Only non-pathogenic organisms remained, and both Escherichia coli and Staphylococcus aureus were destroyed. There was some reduction (less than 50 percent) of the activities of specific antibody to E. coli and lactoferrin, but lysozyme was stable and the pasteurised milk remained effective at inhibiting in vitro growth of E. coli.

Antibodies, Bacterial↗
PubMed1977

Intramuscular iron-dextran and susceptibility of neonates to bacterial infections. In vitro studies.

An increased incidence of E. coli sepsis has been observed in neonates given intramuscular iron-dextran for prevention of iron deficiency. Mechanisms for this apparent effect on susceptibility to infection were investigated by comparing phagocytic and antibacterial functions in paired samples of venous blood from 7 infants, median age 5 days, before and after iron-dextran. Post-treatment sera had increased inhibitory effects on leucocyte chemotaxis and markedly reduced bacteriostatic effects agaainst E. coli. The clinical relevance of the effects on chemotaxis is uncertain. The reduction in serum bacteriostasis is similar to that observed in other forms of hyperferraemia not associated with saturation of transferrin, and is a likely cause of the increased susceptibility to infection in vivo. We consider that prophylactic treatment with parenteral iron-dextran is contraindicated in early infancy.

Anemia, Hypochromic↗
PubMed1976

Perinatal infections by group B beta-haemolytic streptococci.

Since 1970 there has been an increase in isolations of Group B beta-haemolytic streptococci from infants and mothers at the National Women's Hospital and the organism has become the major cause of fatal perinatal infection. Forty-three of 60 stillborn and liveborn infants with postmortem isolations of Group B streptococci had pneumonia and of these a minority also had meningitis and/or septicaemia. Amnionitis was found in 15 of 20 placentae examined from these patients and an ascending infection from the maternal genital tract, often through intact membranes, was considered likely in the majority. However, a review of the prenatal histories of 33 infants showed that only a minority had premonitory features such as prolonged rupture of membranes, prolonged labour or maternal fever. Thirteen of 26 liveborn infants had a birth weight less than 2500 g. The majority presented within one hour of birth with respiratory distress or apnoea and died within 48 hours of birth. Early diagnosis of Group B infection is possible if bacteriological and radiological evidence is sought in infants of low birth weight, with low Apgar scores and with early onset of respiratory distress syndrome or apnoea in addition to those having the more usual indications of intrauterine infection. Group B streptococci were carried vaginally in 9 per cent of women attending an antenatal clinic and this high carrier rate is considered to preclude prophylactic treatment.

Female↗