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Biomedical subjects

G Johnson

Publications and source records attributed to G Johnson.

At least 559 records · Page 31Linked to original sources
PubMed1979

An easily assembled and inexpensive apparatus for continuous monitoring of expired carbon dioxide concentrations in artificially ventilated animals.

An inexpensive and simple apparatus for monitoring expired carbon dioxide concentrations in artificially ventilated animal preparations is described. The system may be rapidly and easily constructed using a standard recording pH electrometer and a commercially available Pco2 electrode. This assembly has been proven to be an effective and sensitive means of monitoring CO2 levels, detecting changes in this gas within one-half percentage.

Animals↗
PubMed1979

Additions to the myotonic dystrophy linkage group.

One hundred and thirty members of a family with 33 cases of Dystrophia myotonica (Dm) were tested for various genetic markers including Km, Jk, Lu and Se. All individuals tested were Lua negative, but many were heterozygous for the other markers. Except for two cases all patients with Dm were positive for Km3 and Jka and they were secretors. Assuming the genes are linked and that the order of the loci is Km, Jk, Lu, Se, Dm, then there were 22 meioses informative for Dm and in 10 of these a recombination must have occurred between two of the five loci. Looking at individual pairs of loci, there were no recombinations between Km and Jk in seven informative meioses, three recombinations out of 10 meioses informative for Jk/Se, no recombinations between Se and Dm in five informative meioses and three recombinations out of 12 meioses informative for Jk/Dm.

Female↗
PubMed1979

Pressure passive cerebral blood flow and breakdown of the blood-brain barrier in experimental fetal asphyxia.

Cerebral blood flow (CBF) was studied in non-exteriorized near-term sheep fetuses using the radioactive microsphere technique. By partially occluding the umbilical vessels for a period of 1--1 1/2 hours a progressive and severe asphyxia with a final arterial pH of 6.90 was achieved. Varying the mean arterial blood pressure in the fetuses by blood withdrawal or infusion in this state, CBF was measured at different perfusion pressures (mean arterial blood pressure (MABP) minus central venous pressure (CVP)). A passive flow/pressure relationship--loss of autoregulation--was found, with hyperemia reaching CBF values up to 6 times normal at normal MABP of about 60 to 70 mmHg, and severe ischemia reaching CBF values close to zero in large cortical areas at MABP of 30 mmHg. CVP remained essentially unchanged at 10--15 mmHg. The severe and prolonged asphyxia rendered the blood-brain barrier leaky to the albumin tracer Evans blue. In four other fetuses umbilical cord clamping was omitted. However, only in one of these cases was acidosis completely avoided, and CBF autoregulation maintained. The three other fetuses were acidotic at the end of the surgical procedure and had impaired autoregulation.

Animals↗
PubMed1979

Transmission and control of dentinal pain: resin impregnation for the desensitization of dentin.

With the exception of direct electrical stimulation, it seems that all procedures known to produce dentinal pain may mechanically distort the structure of pain-sensitive nerves in the pulp and predentinal area and that this effect is mediated by a hydrodynamic link. Nature may contribute to insensitive dentin by: production of irregular, atubular dentin at the pulpal wall; obliteration of dentinal tubules by sclerosis; and mineralization of a superficial layer, pellicle or plaque, at the exposed surface. Few clinical methods are capable of accelerating these mechanisms. A technique of resin impregnation for the desensitization of exposed dentin has been presented. After proper pretreatment, that includes drying the dentin surface, resin tags can be obtained in the outer part of the dentinal tubules and may immediately and permanently relieve dentinal pain. This technique seems to be a good alternative to other methods, especially for patients with occlusal or incisal exposures caused by abrasion, grinding, or fracture, in which other methods cannot provide immediate and long-lasting desensitization.

Acid Etching, Dental↗
PubMed1978

Myotonia dystrophica: obstetric complications.

We describe the course and outcome of 23 pregnancies in six women affected by myotonia dystrophica in a large Labrador family. A seventh patient had 14 pregnancies, so that the infertility commonly described in this disorder did not apply to this family. The rate of complications was high, particularly in respect of polyhydramnios, premature onset of labor, cesarean section, postpartum hemorrhage, and neonatal deaths. Polyhydramnios indicated that the fetus was abnormal. Direct observation of an atonic uterus at cesarean section supported other evidence that uterine muscle may be affected. We also report a newborn infant with the congenital form of myotonic dystrophy, a manifestation which has been attributed to the effect of a maternal intrauterine factor upon a fetus carrying the gene.

Female↗
PubMed1978

Myotonia dystrophica: unusual features in a Labrador family.

A large family with myotonia dystrophica has been recognized in an isolated area of Labrador. The complete family tree showed 29 of 108 members to be affected, including an infant with the congenital form of the disease. The propositus presented with epiphora and reduced frequency of blinking, with incomplete closure--features that have not previously been stressed. Ten of the younger affected persons had no lens opacities, although most had systemic muscle signs. Slit-lamp examination was therefore not a valuable method of early detection of the disease in the family. Many of the women affected by myotonia dystrophica had obstetric complications, particularly hydramnios, premature onset of labour, necessity for cesarean section, postpartum hemorrhage and neonatal death. Hydramnios was associated in each instances with perinatal death. The fetus in each case of hydramnios may have had the gene for myotonia dystrophica. Immunoglobulin A concentrations were reduced significantly in 27 affected persons in comparison with 77 unaffected family members. There were no such differences for the other immunoglobulin classes.

Adolescent↗
PubMed1978

Studies of cyclic AMP action using mutant tissue culture cells.

S49 mouse lymphoma cell mutants, each with a specific defect in its ability to generate or respond to cyclic AMP, have been isolated. Analysis of the properties of these cells has begun to provide information on complex and significant biologic problems related to the cyclic AMP system.

Adenylyl Cyclases↗