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Biomedical subjects

M Lawrence

Publications and source records attributed to M Lawrence.

At least 109 records · Page 6Linked to original sources
PubMed1980

Endocochlear potential and scala media oxygen tension during partial anoxia.

The endocochlear potential and the scala media oxygen tension were measured from the basal coil of the guinea pig cochlea during levels of partial respiratory anoxia. This was accomplished by simultaneously positioning two electrodes (for endocochlear potential and PO2) into the endolymph by a transbasilar membrane approach, in order to minimize blood capillary damage. The intracochlear pO2 was stable until the respiratory oxygen concentration was reduced to 16 per cent on the average. Thereafter, a further reduction of oxygen in the respiratory mix reduced both the endolymph pO2 and the endocochlear potential. The coupling between the endocochlear potential and endolymph pO2 is proportional over a 70 to 80 per cent reduction in endolymph pO2, and at this point the endocochlear potential is reduced by 50 per cent. For partial levels of respiratory oxygen that are not too low (e.g., > 12 per cent oxygen) it is possible to maintain partial levels of intracochlear pO2 for at least six minutes. During this time period the endocochlear potential is also held at a stable but reduced level.

Animals↗
PubMed1980

Control mechanisms of inner ear microcirculation.

Some disease processes, drugs, and noise are said to produce vascular disorders of the inner ear, and in some instances changes in the capillaries have been observed during histologic examination of the temporal bones. Consequently the ability to control the circulation is important because of its therapeutic implications. This brief review points out the areas of conflicting experimental evidence and some of the factors that may be responsible for the variations.

Animals↗
PubMed1979

Intracellular potential changes of Corti's organ with anoxia.

Intracellular measurements of the resting cell membrane potentials of guinea pig Corti's organ were made in order to determine the sensitivity of this cell potential to anoxic hypoxia (a lowered oxygen state due to lack of respiratory oxygen) and to establish differences according to cell types or morphologic regions of the sensory epithelium. The negative cell potentials measured from successful electrode penetrations were found to be relatively more stable and resistant to change during a 120-s period of anoxia than was the positive endocochlear potential. The intracellular resting potentials were also much slower to recover after resumption of respiration. Data obtained from various cells in two different regions of Corti's organ is receiving oxygen from both the perilymph and the endolymph. An iontophoretic dye-marking technique was used to label some experimental cells for later histologic identification.

Action Potentials↗
PubMed1979

Use of albumin gradients for X and Y sperm separation and clinical experience with male sex preselection.

Semen samples obtained from 18 normal males and 37 husbands requesting male child preselection were separated on concentration gradients of human serum albumin. Separated semen obtained from the husbands was then used for artificial homologous insemination (AIH). A significant increase in the sperm motility, progressive drive, and percentage of Y-bearing sperm along with a decrease in the total sperm count and percentage of abnormal forms were observed in separated specimens. Fathers of three or more female children had a slightly smaller but statistically significant percentage of Y-bearing sperm in their semen samples than did normal males. Ten conceptions were achieved with separated semen. Seven pregnancies terminated in normal deliveries of five male and two female infants, one ended in a spontaneous abortion of a male fetus, and two patients are still expecting. The ratio of male to female conceptions in this small study parallels the ratio of Y to X sperm in the final specimen used for AIH.

Adult↗
PubMed1979

Artificial insemination homologous with oligospermic semen separated on albumin columns.

Semen samples obtained from 27 infertile men were separated on human serum albumin (HSA) columns prior to artificial homologous insemination (AIH). The columns contained either a single 7.5% HSA layer or two 17.5% and 7.5% HSA layers. Separated specimens were free of seminal debris, had significantly improved motility and progressive drive, and had a decreased percentage of abnormal forms. The total sperm count was also significantly decreased after separation, especially with the two-layer technique. No conceptions occurred in 21 couples when two-layer separation was used, but four pregnancies in 12 couples resulted from AIH with semen separated on the single-layer column. The mean total count of motile sperm obtained for AIH was 5 million with the two-layer and 31 million with the one-layer technique.

Adult↗
PubMed1978

Money for old rope.

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Education, Medical, Graduate↗