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L Sagan

Publications and source records attributed to L Sagan.

10 recordsLinked to original sources
PubMed2001

An unusual stab wound of the cervical spinal cord: a case report.

STUDY DESIGN: A rare case of a laterally directed stab wound injury of the cervical spinal cord is reported. OBJECTIVE: To describe the unusual mechanism of injury of this case and its clinical features. The surgical indications for penetrating injuries of the spinal cord are discussed. SUMMARY OF BACKGROUND DATA: Spinal stab wound injuries are rare, and the literature on the subject is scant. There has been only one large clinical review from South Africa, published in 1977. The clinical features and the injury mechanism of a laterally directed stab wound to the cervical spine have not been previously described. METHODS: An 18-year-old man was stabbed in the right side of the neck at C1-C2. The blade penetrated the spine laterally and went through the ligaments without affecting the bony structures. On admission the patient had tetraplegia and was in respiratory failure. Radiologic investigation showed the retained blade passing through the cord but showed no bony or vascular injuries. RESULTS: Before extraction, the knife was followed to its tip with careful dissection. Because no cerebrospinal fluid leak was noted in the area, the dura was not exposed. After surgery, magnetic resonance images showed a complete transection of the spinal cord at C1-C2. The patient was neurologically unchanged in follow-up examinations. CONCLUSION: Laterally directed horizontal stab wounds of the spine are particularly dangerous because the blade can pass between two vertebrae to transect the cord. The neurologic injury that results is irreversible. The more common stab wounds, inflicted from behind, usually produce incomplete cord damage.

Adolescent↗
PubMed1993

On the origin of mitosing cells. 1967

A theory of the origin of eukaryotic cells ("higher" cells which divide by classical mitosis) is presented. By hypothesis, three fundamental organelles: the mitochondria, the photosynthetic plastids and the (9+2) [9(2)+2] basal bodies [kinetosomes] of flagella [undulipodia] were themselves once free-living (prokaryotic) cells. The evolution of photosynthesis under the anaerobic [anoxic] conditions of the early atmosphere to form anaerobic bacteria, photosynthetic bacteria and eventually blue-green algae (and protoplastids) is described. The subsequent evolution of aerobic metabolism in prokayotes to form aerobic bacteria (protoflagella [undulipodia] and protomitochondria) presumably occurred during the transition to the oxidizing atmosphere. Classical mitosis evolved in protozoan-type cells millions of years after the evolution of photosynthesis. A plausible scheme for the origin of classical mitosis in primitive amoeboflagellates [amoebomastigotes] is presented. During the course of the evolution of mitosis, photosynthetic plastids (themselves derived from prokaryotes) were symbolically acquired by some of these protozoans to form the ["eukaryotic" deleted] algae and the green plants. The cytological, biochemical and paleontological evidence for this theory is presented, along with suggestions for further possible experimental verification. The implications of this scheme for the systematics of the lower [smaller] organisms is discussed.

Animals↗
PubMed1975

+Gz tolerance in man after 14-day bedrest periods with isometric and isotonic exercise conditioning.

The purpose of this study was to determine the effects of isometric or isotonic exercise training on post-bedrest +Gz tolerance. Seven male volunteers, 19-22 years, underwent accelerations of +2.1 Gz (740 s), +3.2 Gz (327 s), and +3.8 Gz (312 s) in a selected, randomized order; the ramp to peak acceleration was 1.8 G/min. The centrifugation runs were terminated by loss of central vision (blackout) to a white light with a luminance of 3.15 times 10-5 log candle/cm-2 (0.092 ft-lambert). The study began with a 14-d ambulatory control period, followed by three 14-d bedrest periods (each separated by a 21-d recovery period) and then a final week of recovery. During the ambulatory periods, the subjects exercised on a bicycle ergometer at 50% of their maximal oxygen uptake (max VO2) for 1 h/d. During two of the three bedrest periods, the subjects performed in the supine position one of two routines, either isometric exercise (21% of max leg extension force for 1 min followed by 1-min rest) or isotonic exercise (68% of max VO2) for 0.5 in the morning and afternoon. During the third bedrest period, no exercise was performed. In general +Gz tolerance was reduced by 24% to 35% (p less than or equal to 0.05) after bedrest. Compared with control values, there were significant reductions in average tolerance times after bedrest with no exercise and isotonic exercise at all G levels. With isometric exercise, there was a significant decrease in tolerance at 2.1 Gz but not at 3.2 Gz or 3.8 Gz, even though the latter tolerances were reduced 15.6% and 10.0%, respectively. Both exercise regimens maintained tolerance at levels equal to or above that obtained with no exercise. Compared with control values, average tolerances were lower (p less than or equal to 0.05) after the two recovery periods between the bedrest periods (minus 24% to minus 26% at 3.2 Gz and 3.8 Gz), indicating that 3 weeks of ambulation was not sufficient time for full recovery from the deconditioning induced in this study. A prediction equation was constructed with data from all comparable studies utilizing deconditioned men riding relaxed without protective garments: Tolerance (in seconds) equals minus 334 + (1715/+Gz level). From this equation, the calculated tolerance after bedrest is 13.5 min at 1.5 G, and the point of zero tolerance is 5.1 Gz.

Acceleration↗
PubMed1967

On the origin of mitosing cells

A theory of the origin of eukaryotic cells ("higher" cells which divide by classical mitosis) is presented. By hypothesis, three fundamental organelles: the mitochondria, the photosynthetic plastids and the (9+2) basal bodies of flagella were themselves once free-living (prokaryotic) cells. The evolution of photosynthesis under the anaerobic conditions of the early atmosphere to form anaerobic bacteria, photosynthetic bacteria and eventually blue-green algae (and protoplastids) is described. The subsequent evolution of aerobic metabolism in prokaryotes to form aerobic bacteria (protoflagella and protomitochondria) presumably occurred during the transition to the oxidizing atmosphere. Classical mitosis evolved in protozoan-type cells millions of years after the evolution of photosynthesis. A plausible scheme for the origin of classical mitosis in primitive amoeboflagellates is presented. During the course of the evolution of mitosis, photosynthetic plastids (themselves derived from prokaryotes) were symbiotically acquired by some of these protozoans to form the eukaryotic algae and the green plants. The cytological, biochemical and paleontological evidence for this theory is presented, along with suggestions for further possible experimental verification. The implications of this scheme for the systematics of the lower organisms is discussed.

Animals↗
PubMedDate not supplied

[Spinal reflexes in the determination of brain death].

The authors present the results of spinal cord function evaluation in organ donors by examination of reflexes. The knee reflex and ankle jerk, as well as abdominal reflex and foot withdrawal reaction were tested in 31 donors. At least one of the above was seen in 25 individuals. It is suggested on the basis of data obtained not to hamper the transplant procedure in cases of tested reflex persistency when brain death is revealed on relevant examination.

Adolescent↗
PubMedDate not supplied

[Brain stem auditory evoked potentials in brain death state].

The authors studied auditory brainstem evoked potentials (BAEP) in 27 organ donors aged 40 to 68 years treated in neurosurgery units in Szczecin and Grenoble. Abnormal results were found in all cases. In 63% of cases no evoked action potentials were obtained, in 34% only the 1st wave was obtained, and in two cases evolution was observed with activity extinction. The authors believe that in the process of shaping of BAEP morphotic extinction begins from the later waves to earlier ones in agreement with the rostrocaudal direction of extinction of the functions or brain midline structures, and in a single study various findings may be obtained.

Adult↗