Hyperbaric oxygen decreases infarct size and behavioral deficit after transient focal cerebral ischemia in rats.

Cerebral hypoxia is a major component of immediate and secondary cell damage caused by ischemia. Hyperbaric oxygen (HBO) is a potent means to increase the amount of oxygen dissolved in blood plasma. The effectiveness of HBO in clinical and experimental cerebral ischemia, however, is controversial. We sought to determine whether treatment with HBO initiated early after focal cerebral ischemia-onset protects the brain when experimental conditions such as brain temperature are controlled. Male Wistar rats (n=57) underwent reversible filament occlusion of the right middle cerebral artery (MCA) for 75 min. Animals were awakened after filament introduction and assessed for presence of forelimb paresis. Rats then underwent a 60-min course of either 100% O(2) at 1.0 atmosphere absolute (ata; control group), HBO 1.5 ata, or HBO 2.5 ata in a customized HBO chamber allowing physiological monitoring and pericranial temperature control. The filament was then removed. Seven days after ischemia, rat behavior was scored from 3-18 (18=normal) and brains were removed for histological analysis of infarct volume. Rats treated with HBO 2.5 ata had better mean+/-standard deviation (S.D.) behavioral scores (14+/-2; p<0.05) than control (10+/-3) or HBO 1.5-ata-treated animals (11+/-3). Similarly, total infarct volumes (mean+/-S.D.) were smaller in animals receiving HBO at 2.5 ata (76+/-65 mm(3); p<0.05) compared to control (129+/-83 mm(3)) and HBO 1.5-ata (119+/-68 mm(3))-treated groups. Cortical infarction occurred less frequently in HBO 2. 5-ata-treated than in control animals (44% vs. 71%; p<0.05). We conclude that HBO can improve outcome after temporary focal ischemia when treatment is started early after ischemia-onset but HBO dose appears important. Potential mechanisms include enhanced oxygen supply to marginally perfused cells.

Effects of postischemic halothane administration on outcome from transient focal cerebral ischemia in the rat.

This study examined the effect of prolonged postischemic halothane administration on outcome from transient focal cerebral ischemia in rats. Conscious normothermic rats were subjected to 75 minutes of filament middle cerebral artery occlusion (MCAO). Animals were then divided into two groups. The Awake group (n = 15) remained awake following ischemia. The Halothane group (n = 15) received 1.3-1.4% halothane for 5 hours after onset of recirculation. In both groups, brain temperature was maintained at 37.5 degrees C during ischemia and the first 22 hours of recovery. Seven days after ischemia, the severity of hemiparesis and cerebral infarct size were examined. Neurologic scores did not differ between groups (Awake = 1+/-2.75; Halothane = 2+/-2; p = 0.772, median +/- interquartile range). Neurologic scores and total infarct volumes were correlated (R = 0.653; p = 0.0004). Cortical (Awake = 76+/-57 mm3; Halothane = 90+/-57 mm3; p = 0.494, mean +/- standard deviation), subcortical (Awake = 71+/-33 mm3; Halothane = 80+/-35 mm3; p = 0.472), and total (Awake = 147+/-88 mm3; Halothane = 171+/-91 mm3; p = 0.477) infarct volumes were not significantly different between groups. The data indicate that postischemic halothane administration offers no benefit in ameliorating damage from focal cerebral ischemia. This suggests that the neuroprotective effect of halothane observed in other studies is consistent with influences on intra-ischemic pathophysiology only.

Electroencephalographic burst suppression is not required to elicit maximal neuroprotection from pentobarbital in a rat model of focal cerebral ischemia.

BACKGROUND: Barbiturates have previously been demonstrated to reduce focal cerebral ischemic brain damage. However, the dose of drug required to elicit maximal neuroprotection has not been defined. The authors' hypothesized that doses of pentobarbital substantially lower than those required to cause electroencephalographic burst suppression would result in maximal magnitudes of reduction of cerebral infarct volume. METHODS: Wistar rats underwent 90 min of filament occlusion of the middle cerebral artery while either awake (control), or anesthetized with intravenous sodium pentobarbital administered to preserve an active electroencephalogram (15-23 mg.kg-1.h-1) or a pattern of burst suppression (45-60 mg.kg-1.h-1; n = 17). During ischemia and for the first 6 h of recirculation, brain temperature was rigorously controlled at 38.0 +/- 0.2 degrees C. Rats were allowed a recovery interval of 7 days after which neurologic function and cerebral infarct volume were assessed. In nonischemic rats undergoing a similar anesthetic protocol, the cerebral metabolic rate of glucose utilization was measured at each anesthetic depth. RESULTS: Relevant physiologic values were similar between groups. Total infarct volume (mean +/- SD) was smaller in the active electroencephalogram group than in the control group (124 +/- 68 mm3 versus 163 +/- 66 mm3; P < 0.05). Increasing the dose of pentobarbital (burst suppression) did not further decrease infarct volume (128 +/- 54 mm3). Neurologic score and infarct volume were positively correlated (P < 0.001). Cerebral metabolic rate of glucose utilization was reduced by 56% in the burst suppression group versus 43% in the active electroencephalogram pentobarbital group (P < 0.001). CONCLUSIONS: Sodium pentobarbital administered at either dose (active electroencephalogram or burst suppression) resulted in an approximately equal to 25% reduction of cerebral infarct size, indicating that burst suppression is not required to elicit maximal neuroprotective efficacy.

Halothane reduces focal ischemic injury in the rat when brain temperature is controlled.

BACKGROUND: Previous work has demonstrated that rats anesthetized with halothane during focal cerebral ischemia have better histologic and neurologic outcome than do rats undergoing the same insult when awake. The purpose of this experiment was to determine whether this difference persists when brain temperature is held similar in halothane-anesthetized and awake experimental groups. METHODS: Two ischemia experiments were performed. In both, the middle cerebral artery was occluded for 90 min. Temperature was monitored from a radiotelemetered thermistor implanted in the cerebral cortex. Four days after ischemia, infarct volume and neurologic function were assessed. In experiment 1, brain temperature was not controlled in awake rats. Temperature in rats anesthetized with halothane, approximately 1 minimum alveolar concentration, was regulated by servomechanism by surface heating or cooling to replicate the temperature profiles generated by awake animals. To address methodologic issues regarding infarct volume analysis, a subset of nine rats was examined for the effect of the histologic staining technique and the mathematical modeling algorithms used for computation of infarct volume values. In experiment 2, the brain temperature of awake and halothane-anesthetized rats was maintained normothermic (38.0 degrees C) throughout ischemia and early recirculation. RESULTS: In experiment 1 no difference between groups was observed for cortical (halothane 146 +/- 95 mm3 and awake 126 +/- 108 mm3; P = 0.64) or subcortical (halothane 110 +/- 48 mm3 and awake 100 +/- 66 mm3; P = 0.66) infarct volume. Neurologic function was also similar between groups. Total infarct volume was approximately 11% greater when histologic sections were stained with hematoxylin and eosin than when they were stained with nitro blue tetrazolium, although volumes correlated closely between the two techniques (r2 = 0.996). Analysis by orthogonal or frustum projection from two-dimensional planimetric areas to three-dimensional volumes resulted in nearly identical values (r2 = 0.999). In experiment 2, halothane-anesthetized rats experienced a 46% reduction in cortical infarct volume (halothane 106 +/- 97 mm3 and awake 197 +/- 103 mm3; P = 0.03). The incidence of hemiparesis was reduced in the anesthetized group (P = 0.03). CONCLUSIONS: When brain temperature was maintained normothermic throughout the focal ischemic insult, a neurologic and histologic protective effect for halothane anesthesia was observed. This effect of halothane was not sufficient to persist when large variations in brain temperature were allowed. Regulation of brain temperature is a critical factor in the determination of the effects of anesthetics on focal ischemic brain damage.

Apocrine differentiation in human mammary carcinoma.

Six invasive carcinomas that contained apocrine differentiation as the primary morphologic pattern were selected from a series of 1500 prospectively examined breast carcinomas (0.4%). While apocrine features were seen in many breast tumors, these six cases were identified by uniformly fine granular, pale, eosinophilic cytoplasm with apical cytoplasmic projections similar to that seen in apocrine metaplasia. In each example, ultrastructural analysis revealed the presence of numerous 400-600 nm membrane bound vesicles with dense homogeneous osmophilic cores. These granules clustered toward the apex of the cytoplasm in the majority of the epithelial cells. All six tumors were deficient in high-affinity, low-capacity 8S estrogen and progesterone proteins, while a high-capacity, low-affinity, nonsaturable 4S progesterone-estrogen binding protein was observed. Cortisol did not bind to this protein. These observations characterize the ultrastructure of apocrine carcinoma as a variant of human mammary carcinoma.

Adenosquamous differentiation in mammary carcinoma: an ultrastructural and steroid receptor study.

Five breast carcinomas with only squamous morphology by light microscopy demonstrated ultrastructural features of both squamous and adenomatous differentiation within the same individual cells. Two of the five cases demonstrated quantitatively low levels of saturable estrogen- and/or progesterone-binding proteins. In no case were there quantitative or qualitative patterns of receptors indicative of clinical hormonal response potential. It is suggested that primary squamous cell carcinomas of the breast should be examined ultrastructurally for adenosquamous differentiation as each of the five apparent squamous carcinomas observed in a prospective study of 1,760 (0.3%) cases of breast cancer demonstrated adenosquamous differentiation ultrastructurally.