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Biomedical subjects

A Bass

Publications and source records attributed to A Bass.

At least 37 records · Page 2Linked to original sources
PubMed1997

Transiently increased basilar artery flow velocity following severe head injury: a time course transcranial Doppler study.

BACKGROUND AND PURPOSE: Transcranial Doppler ultrasonography has been used to study changes in cerebral hemodynamics following head injury. However, most studies evaluated the anterior circulation and little information exists on transcranial Doppler of the vertebrobasilar arteries after head injury. METHODS: Thirty-two patients with a Glasgow Coma Scale (GCS) score between 4-8 and 11 patients with a GCS score between 9-14 were studied using transcranial Doppler ultrasonography for the first 10 days after injury. Daily variations in the mean blood flow velocities of all major cerebral arteries were recorded. RESULTS: In patients with GCS score between 4-8, the mean blood flow velocities in the middle cerebral and basilar arteries gradually increased beginning on day 2 postinjury and peaked on the 4th-5th day after injury. Those changes were more prominent, and appeared earlier, in the basilar artery. The ratio between the mean flow velocities of the middle cerebral artery and the basilar artery during the first 4 days was significantly lower than in normal controls, indicating a particular increase of flow velocity in the basilar artery. Nineteen out of 32 patients (60%) with severe head injury showed mean blood flow velocity increased over 75 cm/sec in the basilar artery. Mean blood flow velocity >90 cm/sec in the basilar artery, compatible with vasospasm, was observed in 12 of 32 patients (37%). Spasm in the middle cerebral artery was observed in 12 (37%) of patients; 10 of them also had evidence of basilar artery spasm. On the whole, 14 of 32 (43%) patients had evidence of spasm either in the middle cerebral or basilar arteries or in both. In 5 of 11 patients (50%) with moderate head injury (GCS score 9-14), blood flow velocity in the basilar artery greater than 75 cm/sec was observed, but in only two of them it reached the values over 90 cm/sec. Vasospasm in the middle cerebral artery was noted in one patient. CONCLUSIONS: A significant number of patients develop increased flow velocities compatible with vasospasm in the basilar artery after severe head injury. This phenomenon may represent an additional factor that contributes to the poor outcome of severely head-injured patients.

Adolescent↗
PubMed1997

The problem of "concreteness".

"Concrete" patients manifest resistance to interpretation per se. Their apparently primitive thinking is the result of complex psychodynamics, explicable in terms of the mechanisms of wish fulfillment and a revised theory of fetishism. The general thesis is that an unconscious equation of differentiation with overwhelming tension leads to a global process of defense against the differentiating function of the analytic frame. The wider implications of this theory can be integrated with Freud's mostly unknown late attempt to generalize the theory of fetishism.

Fetishism, Psychiatric↗
PubMed1996

Vascular complications of total abdominal perfusion and aortic stop-flow infusion.

During a 2 year period (1992-1993), 149 patients with advanced abdominal cancer underwent total abdominal ischemic perfusion (TAP) and stop-flow infusion (SFI) 159 times in an attempt to achieve palliation. These procedures and aortic stop-flow infusion require insertion of balloon catheters into the abdominal aorta and inferior vena cava by a transfemoral approach. Flow is arrested for 15 minutes, during which time chemotherapeutic agents are infused into the aorta, distal to the balloon occlusion. Femoral access is by a surgical incision. The passage of the catheters is guided by fluoroscopy. Some tumor response was observed in 35% of the patients. Ten patients had major vascular complications; two iliac artery aneurysms were lacerated and required emergency repair. There were two femoral artery false aneurysms that required surgical correction, one early and one late. Aortic dissection was detected in four patients, but these did not require surgical intervention. Two patients had thrombosis distal to the occluded vessel, both required surgical intervention. To reduce the incidence of these vascular complications we recommend: (1) a clinical and vascular laboratory evaluation before the procedure, and (2) angiography of normal flow in patients with underlying vascular disease.

Abdominal Neoplasms↗
PubMed1995

A software toolkit for hierarchical task analysis.

This paper describes a prototype software tool that offers support to the human factors specialist using hierarchical task analysis (HTA). The tool provides a direct manipulation diagram editor for HTA and provides high-quality output of analyses, in both graphic and automatically generated tabular form. The tool is implemented in Smalltalk-80 and currently runs on Macintosh computers.

Journal Article↗
PubMed1994

Aspects of urethrality in women.

It has long been noticed that women experience direct sexual stimulation from urethral practices that men do not. However, this empirical finding remains to be integrated with the general theory of female psychosexual development. An attempt is made to begin such an integration, with a focus on urethral perversions or perverse trends.

Adult↗
PubMed1993

Interruption of vascular thrombosis by bolus anti-platelet glycoprotein IIb/IIIa monoclonal antibodies in baboons.

PURPOSE: Because the platelet membrane receptor glycoprotein IIb/IIIa plays a central role in the recruitment of platelets into forming thrombus, therapeutic inhibition of this receptor complex may be particularly useful to prevent thrombosis after small vessel arterial manipulation. METHODS: The relative hemostatic safety and antithrombotic efficacy for thrombus formation at sites of endarterectomy and implanted prosthetic vascular graft of a murine monoclonal antibody (LJ-CP8) against platelet glycoprotein IIb/IIIa have been determined in baboons after bolus injections in doses (10 mg/kg) that block platelet receptor function for fibrinogen and other adhesive glycoproteins (absent platelet aggregation and bleeding times > 30 minutes without affecting circulating platelet counts). RESULTS: Thrombus formation was eliminated by LJ-CP8 at sites of surgical endarterectomy in fresh segments of homologous aorta incorporated into chronic exteriorized arteriovenous femoral shunts (accumulation of indium 111-labeled platelets fell from 4.40 +/- 0.89 x 10(9) platelets/cm in control animals [n = 6] to 0.23 +/- 0.01 x 10(9) platelets/cm in treated animals [n = 4]; p < 0.005). The formation of thrombus was also abolished by LJ-CP8 at sites of 1 cm prosthetic vascular grafts (4 mm inner diameter polytetrafluoroethylene grafts) interposed into common carotid arteries (deposition of indium 111-labeled platelets decreased from 2.57 +/- 0.43 x 10(9) platelets/cm [n = 5] to 0.16 +/- 0.06 x 10(9) platelets/cm, [n = 4]; p = 0.004). However, LJ-CP8 injections produced substantial bleeding in the surgical wound during the first few hours after operation. Thirty days after operation all four graft implants were patent in JJ-CP8-treated animals compared with two of five in control animals (p = 0.06). CONCLUSIONS: We conclude that profound inhibition of platelet glycoprotein IIb/IIIa receptor function by single bolus injection of LJ-CP8 monoclonal antibody transiently abolishes platelet hemostatic function, eliminates acute thrombus formation at sites of endarterectomy and prosthetic vascular graft implants, and may improve vascular patency.

Animals↗
PubMed1993

Interruption of vascular thrombus formation and vascular lesion formation by dietary n-3 fatty acids in fish oil in nonhuman primates.

BACKGROUND: Because of discrepant claims regarding the relative biological effects of n-3 fatty acids (n-3FAs), we have concurrently measured the effects of dietary n-3FAs on blood and vascular lipid composition, hemostatic function, blood thrombotic responses, vascular thrombus formation, and vascular lesion formation in baboons. METHODS AND RESULTS: Dietary n-3FAs displaced n-6FAs in plasma, platelets, blood vessels, and corresponding urinary eicosanoid metabolites (p < 0.01 in all cases) within weeks after initiation of a semipurified diet containing 1 g/kg per day n-3FA-ethyl ester concentrate (composed of two thirds eicosapentanoic acid and one third docosahexanoic acid). Coincidentally, platelet hemostatic function became minimally impaired (template bleeding times prolonged from 4.3 +/- 0.5 minutes to 7.6 +/- 1.3 minutes, p = 0.039); concentrations of collagen producing half-maximal platelet aggregation increased (from 6.4 +/- 2.1 to 8.5 +/- 2.5 micrograms/mL, p = 0.045); and tissue factor expression by endotoxin-stimulated blood monocytes fell (from 6.5 +/- 1.2 to 1.7 +/- 0.14 mU/10(6) cells, p < 0.005). Dietary n-3FAs decreased deposition of platelets onto thrombogenic segments of Dacron vascular graft incorporated into chronic exteriorized femoral arteriovenous (AV) shunts, a thrombotic process resistant to the effects of both aspirin and heparin (111In-labeled platelet deposition decreased from 14.1 +/- 1.4 x 10(9) platelets/5-cm segment at 40-60 minutes with occlusion to 7.5 +/- 0.8 x 10(9) platelets/5-cm segment without occlusion; p < 0.001). Platelet deposition onto segments of endarterectomized homologous normal aorta in the AV shunts of n-3FA-treated animals was similarly reduced (from 4.4 +/- 0.9 to 1.8 +/- 0.4 x 10(9) platelets; p < 0.01). Dietary n-3FAs interrupted vascular thrombus formation at sites of surgical carotid endarterectomy (platelet deposition, 1.5 +/- 0.4 versus 4.4 +/- 1.0 x 10(9) platelets in untreated controls; p < 0.001). Moreover, endarterectomized aortic segments (EASs) from n-3FA-treated donors exhibited little capacity to induce thrombus formation when tested in the AV shunts of control recipient animals (0.24 +/- 0.10 versus 4.4 +/- 0.90 x 10(9) platelets). However, in the converse crossover experiments, EASs from control animals actively accumulated platelets when studied in the AV shunts of n-3FA-treated animals (1.8 +/- 0.4 x 10(9) platelets; p < 0.01 versus n-3FA-treated EASs in shunts of normal animals). Dietary n-3FAs also abolished vascular lesion formation at sites of carotid endarterectomy 6 weeks after surgery (cross-sectional area of neointima 0.048 +/- 0.031 mm2 compared with 0.428 +/- 0.104 mm2 in control arteries; p = 0.010). CONCLUSIONS: In nonhuman primates, dietary n-3FAs in high doses eliminate both vascular thrombus formation and vascular lesion formation after mechanical vascular injury while largely sparing hemostatic function and modestly reducing blood thrombotic responses. These effects are attributed to selective n-3FA-dependent alterations in cellular membrane functions.

Animals↗
PubMed1993

Exteriorized chronic aorto-caval arteriovenous access shunts in the baboon (Papio cynocephalus).

A chronic arteriovenous (AV) blood access shunt has been developed in baboons. It is composed of silicone rubber tubing extensions bonded to vascular graft polytetrafluoroethylene (ePTFE) cuffs, for creating anastomoses with the distal aorta and inferior vena cava. Following surgical implantation, shunts remain patent for months (X = 9 +/- 2.5 months) and provides long-term ex vivo access to non-anticoagulated blood (Mean Blood Flow = 312 +/- 69 mL/min).

Animals↗
PubMed1993

Differences between atrial and ventricular energy-supplying enzymes in five mammalian species.

The purpose of this study was to compare a pattern of 7 enzymes of energy-supplying metabolism in atrial and ventricular myocardium in some mammalian species. Tissue samples of right and left atria and ventricles were obtained from adult male rats, guinea-pigs, rabbits, dogs and pigs. The results clearly demonstrate significant differences in enzyme activities between the atria and ventricles in all these species. In the atria the activity of enzymes connected with aerobic and lactate metabolism (hydroxyacyl-CoA-dehydrogenase, citrate synthase, malate dehydrogenase and lactate dehydrogenase) was markedly lower than in ventricles. On the other hand, in rats, dogs and pigs glucose phosphorylation capacity (hexokinase) was approximately the same in atrial tissue as in ventricles. Right-to-left metabolic differences were much less expressed; conspicuous was only the higher activity of hydroxyacyl-CoA-dehydrogenase in the left atria and ventricles of guinea-pigs and rabbits indicating higher fatty acid utilization capacity in the left heart.

Animals↗
PubMed1992

Laser Doppler flowmetry in lower extremity ischemia: application and interpretation.

The present study was undertaken in order to develop numerical criteria for the parameters of laser Doppler flowmetry-skin blood flow velocity and pulse wave amplitude in the evaluation of lower extremity ischemia. Fifty limbs of young healthy volunteers were examined in order to obtain baseline normal values. Patient population was divided into moderately ischemic (52 limbs) and severely ischemic (22 limbs), based on patients' complaints, physical examination, ankle-brachial indices, pulse volume recordings and arteriographies. Univariate comparison between the three groups of skin blood flow velocity and pulse wave amplitude at each time point were done by analysis of variance. Power of discrimination between degrees of ischemia was evaluated by computing sensitivity and specificity, based on skin blood flow velocity and pulse wave amplitude values at time points best for predicting the severity of disease by multiple regression analysis. Using cutoff points of < 31 for skin blood flow velocity and < 9 for pulse wave amplitude, a 96% sensitivity and 96% specificity were obtained in separating normal from ischemic limbs. Cutoff points of < 9 for skin blood flow velocity and < 4 for pulse wave amplitude discriminated with a 100% sensitivity and specificity between the moderately and severely ischemic limbs. We propose the use of laser Doppler flowmetry with local heating and reactive hyperemia, and the cutoff points stated above as an additional tool to evaluate lower extremity ischemia through assessment of cutaneous microcirculation.

Adult↗
PubMed1992

Dimorphic male brains and alternative reproductive tactics in a vocalizing fish.

Brains and types of behavior among sexually mature vertebrates are portrayed as having two phenotypic states: male and female. However, mating systems and the behavioral tactics employed by the two sexes are far more diverse than conveyed by this simple intersexual dichotomy. For example, in many species, sexually mature males may practice one of two alternative mating tactics. Recent studies of a sound-producing teleost fish now show that intrasexual dimorphism of vocal motor phenotypes among males accompanies the intrasexual divergence of types of reproductive behavior. Thus, one group of males, like females and juveniles, lacks the behavioral, neurophysiological and morphological traits typical of the sexually differentiated vocal motor pathway of the second group. The results are an explicit demonstration that for any one species: (1) alternative mating tactics can be paralleled by alternative phenotypes for the neurons that determine tactic-specific types of behavior, and (2) reproductive maturation is not obligatorily linked to the expression of neuronal secondary sex characteristics.

Animals↗
PubMed1992

Autoimmune mechanisms in thromboangiitis obliterans (Buerger's disease): the role of tobacco antigen and the major histocompatibility complex.

This study is a continuation of our previous work that showed that patients with thromboangiitis obliterans (TAO; Buerger's disease) demonstrate a cell-mediated immune response to human artery type-specific collagens. To investigate the role of cigarette smoking in patients with TAO, cellular and humoral sensitivity was tested to a tobacco glycoprotein (TGP) antigen in 13 patients with Buerger's disease, 16 healthy smokers, and 12 nonsmoking healthy young male subjects. In this study, patients with Buerger's disease and healthy smokers had the same rate of cellular response to TGP, whereas nonsmokers did not respond. All three groups had a 30% to 40% measurable antibody response to TGP. If TGP has an immunologic role in the pathogenesis of TAO, an additional factor (or factors) may be operative. A specific genetic makeup may be one such factor, although at this stage other pathogenic mechanisms cannot be ruled out. Eleven patients with Buerger's disease and two control groups of 10 young healthy smoking male subjects and 12 young nonsmokers underwent histocompatibility leukocyte antigen (HLA) typing. Patients with Buerger's disease had a statistically significantly higher frequency of HLA-DR4 and a significantly lower frequency of the HLA-DRW6 antigen than had both control groups. Because similar findings have been reported in other autoimmune diseases, this observation may serve as further evidence that an autoimmune mechanism is involved in Buerger's disease.

Antibody Formation↗