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Biomedical subjects

R S Kramer

Publications and source records attributed to R S Kramer.

At least 19 recordsLinked to original sources
PubMed1983

Reversible uncoupling of oxidative phosphorylation at low oxygen tension.

The stoichiometry of oxidative phosphorylation at low oxygen tension (less than 3 torr; O2 less than 5 microM) has been measured in rat liver mitochondria. In a steady-state model in which respiration rate was experimentally controlled by either oxygen or substrate (succinate) limitation, flux-dependent variation in the phosphorylation efficiency (P/O ratio) of stimulated mitochondrial respiration was evaluated. P/O ratio remained constant over a wide range of respiration rates in mitochondria limited only by substrate availability. In contrast, oxygen-limited mitochondria demonstrated a continuous decline in P/O ratio as respiration was increasingly restricted. Significant differences in the two test conditions were demonstrated throughout the range of analysis. The effect of oxygen limitation on phosphorylation efficiency was shown to be completely reversed by restoring zero-order kinetics associated with high oxygen tension. These findings are discussed in regard to a proposed uncoupling of mitochondrial coupling site II at low oxygen tension arising as a consequence of energy-dissipating electron flux through the ubiquinone-cytochrome b-c1 region of the respiratory chain (complex III).

Adenosine Diphosphate↗
PubMed1980

Spontaneous regression of prolactin-producing pituitary adenomas.

Two women evaluated for amenorrhea, galactorrhea, and hyperprolactinemia had radiographic changes of the sella turcica (localized erosion on trispiral tomography) suggestive of a pituitary tumor. Both patients experienced spontaneous regression of apparent prolactin-secreting adenomas with a marked decrease in the quantity of galactorrhea and a reduction of serum prolactin concentrations to the normal range. One patient noted a marked improvement of headaches and spontaneous menses resumed in the other patient.

Adenoma↗
PubMed1980

Prolactin-producing pituitary tumors: surgical therapy.

Detection of a prolactin-secreting macroadenoma of the pituitary requires neurosurgical consultation and is almost certainly best resolved by operative removal. In contrast, it is not presently clear whether surgical intervention is appropriate in the majority of patients suspected of harboring microprolactinomas, particularly in view of current uncertainties surrounding the possible antimitogenic properties of bromocryptine. The decision to recommend surgery ordinarily rests on the presumption that certain of these lesions may grow to sufficient size as to represent a permanent threat to the patient's health; other considerations include the patient's desire for fertility and the perceived risk of pregnancy in the presence of a pituitary adenoma. Assuming the patient is sufficiently reliable that we can be assured of the opportunity for regular follow-up evaluations, our group advocates a conservative posture in the majority of women in whom a microprolactinoma is suspected. In any case, it is certainly possible to reassure both the referring gynecologist and the patient that should operative intervention be indicated, the transsphenoidal approach to microprolactinomas of the pituitary is today safe and generally uncomplicated. This is due in no small measure to the contributions of such pioneering neurosurgeons as Guiot, Hardy and, of course, Cushing.

Adenoma↗
PubMed1979

Hypothalamic-pituitary function and radiographic evaluation of women with hyperprolactinemia and an "empty" sella turcica.

A primary "empty" sella may be associated with significant hypothalamic-pituitary dysfunction. This report characterizes the endocrinologic and radiographic findings in six patients with hyperprolactinemia (range 34.3 to 1,170 ng/ml) ultimately found to have an enlarged empty sella. Lateral skull x-ray films and thin-section tomograms were suggestive of pituitary tumors in all patients. Four patients underwent transphenoidal sellar exploration after pneumoencephalography (PEG) failed to demonstrate air within the sella. The inability of PEG to demonstrate an empty sella in two patients was explainable on the basis of an intact diaphragma sellae with previous transient intrasellar pathology responsible for the sellar enlargement. Dynamic hypothalamic-pituitary testing yielded no consistent pattern of response. These studies suggest that an empty sella: (1) may be associated with hyperprolactinemia, regardless of etiology, (2) is not diagnosable by dynamic hormonal testing, and (3) may be indistinguishable from a pituitary tumor by current radiographic techniques.

Adult↗
PubMed1979

Traumatic anterior atlanto-occipital dislocation.

The five cases of atlanto-occipital dislocation reported in the world literature are reviewed, and four additional cases are presented, including two survivors. The pathological anatomy of this potentially catastrophic injury and its management are briefly discussed. Because immediate recognition of the atlanto-occipital dislocation is critical to proper treatment and because the neurological findings are extremely varied, a new radiographic criterion for its identification has been developed.

Adult↗
PubMed1970

Energy and epilepsy.

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Adenosine Triphosphate↗
PubMed1970

Brain adenosine triphosphate: decreased concentration precedes convulsions.

The concentration of adenosine triphosphate in the brain decreased before the onset of generalized convulsions in unanesthetized rats subjected to acute hypoxia or treated with hydroxylamine or pentylenetetrazole (Metrazol). As the convulsive episode continued, adenosine triphosphate decreased further. Stimulation of adenosine triphosphate production forestalled its disappearance from the brain and delayed the development of seizure activity.

Adenosine Triphosphate↗