Diversity in medical school: perceptions of first-year students at four southeastern U.S. medical schools.

PURPOSE: To assess students' perceptions of the extent of diversity in their classes, the role of diversity in their first-year curriculum, and their predictions of the amount of diversity in their future patient populations. METHOD: In 1998, students at four southeastern U.S. medical schools that had distinct demographics and differing institutional missions completed a questionnaire on diversity at the end of the first year. In the instrument, diversity was defined according to nine population characteristics: age, sex, race, ethnic background, physical disability, religious affiliation, sexual orientation, socioeconomic status, and rural background (growing up in a community of less than 5,000). Responses were compared according to students' institution, sex, and race. RESULTS: Questionnaires were returned by 349 of 474 students (74%). Students at the school with the most diverse first-year class placed the greatest value on the contributions of diversity to the learning environment. Women students placed more value on the inclusion of diversity issues in the curriculum than did men students, and they placed greater value on understanding diversity issues in their future medical practices than did men. Compared with Asian American, Hispanic, and white students, African American students were the least likely to think that the curriculum contained adequate information about diversity. CONCLUSIONS: The results indicate that perceptions of diversity were influenced by the students' own demographic characteristics and those of their medical school. The more diverse the class, the more comfortable the students were with diversity and the more they valued its contribution to their medical education.

Changes in profiles of students admitted to Florida allopathic medical schools 1990-1996.

The demographic and academic profiles of first-year classes entering the three allopathic medical schools in Florida (UM, UF, and USF) between 1990 and 1996 have been summarized. In general, the high academic standards for admission (high GPAs and MCAT scores) have been maintained, and in some cases, increased. The percentages of women admitted to the first-year classes at UM and UF have increased in recent years, and the number of women enrolled in MD programs in Florida has increased by 26% since 1990. At the University of Miami, the student body has reached gender parity. There also has been a marked shift in the ethnicity of medical students in the state of Florida. Non-hispanic white students have decreased by 9% to 64.4% of the total population. Black students and hispanic students have made modest gains, and now constitute 7.4% and 11.5% of the population, respectively. Asian students have made the largest gain (6.4%), now making up 15.8% of all Florida medical students. In contrast, there has been no sustained increase in the overall number of underrepresented minority students admitted to first-year classes despite national programs and institutional commitments to do so. These changes have not occurred just at Florida medical schools. They parallel far broader national trends resulting from a dramatic increase in the number of medical school applicants and demographic changes in the applicant pool.

Selective identification of the paternal mitochondrion in living sea urchin eggs and embryos by chlorotetracycline.

When sea urchin eggs are pretreated with fluorescent chelate probe chlorotetracycline (CTC) and then fertilized with unlabeled sperm, a small, brightly fluorescent particle resembling the mitochondrion of free-swimming sperm both in size and fluorescent staining characteristics appears in the egg cytoplasm. This particle first appears near the base of the insemination cone and, like the paternal mitochondrion identified in previous ultrastructural studies, remains closely associated with the male pronucleus during its microtubule-dependent migration toward the egg center. These similarities strongly suggest that the fluorescent particle observed in the cytoplasm of living, CTC-pretreated sea urchin eggs is, in fact, the mitochondrion of the fertilizing sperm.

The effects of inhalation anesthetics on calcium-stimulated exocytosis in a natural membrane model system.

Sea urchin egg cortices were used as an in vitro natural membrane model system to determine the effects of inhalation anesthetics on the Ca2+-regulated exocytotic fusion of cortical vesicles with the egg plasma membrane. When Ca2+ was either absent or present in amounts below the threshold for exocytosis, methoxyflurane, halothane, enflurane, isoflurane, chloroform and fluoroxene, at concentrations up to 5 mM, had no effect on the fusion of cortical vesicles with the plasma membrane. However, when Ca2+ was present at or above threshold levels for exocytosis, each of the tested anesthetics caused an inhibition of cortical vesicle fusion. Exocytosis was inhibited most effectively by methoxyflurane (55%), followed by halothane (30%), while fluoroxene consistently had the least effect (less than 5%). These observations support the view that volatile anesthetics can impair the Ca2+-regulated fusogenic activities of natural membranes and are consistent with other data showing that inhalational agents inhibit secretory processes in intact cells.

Student evaluation of accelerated program at the University of Miami.

The University of Miami School of Medicine has an accelerated, six-year B.S.-M.D. program called the Honors Program in Medicine (HPM). In 1985 the HPM and traditional program students were surveyed at the end of their first year in medical school regarding their opinions about accelerated medical education. Eighty-seven percent of the traditional students felt that HPM students had ability equal to that of the average medical student (that is, neither more nor less ability), but 41 percent felt that the HPM students were less mature than the average class member. The traditional students felt the HPM students were required to follow a rigid collegiate curriculum (76 percent) and had an inadequate nonscience background (68 percent) and that the HPM would negatively affect both the future professional competence of HPM participants (59 percent) and the medical profession (34 percent). A larger percentage of the HPM than the traditional students (63 versus 48 percent) reported earning more than a minor in nonscience subjects, and fewer HPM than traditional students (9 versus 36 percent) felt that pressure to maintain a high grade-point average limited their selection of college courses. The HPM students felt that they were well prepared for medical school academically (82 percent) and emotionally (91 percent). The HPM students excelled academically in college and in the preclinical curriculum.

Effects of the volatile anesthetic halothane on fertilization and early development in the sea urchin Lytechinus variegatus: evidence that abnormal development is due to polyspermy.

The volatile anesthetic halothane, when present at fertilization, dose-dependently increases the incidence of abnormally developing sea urchin embryos at the first cell division. Microscopic examinations of eggs stained with aceto-orcein or the DNA fluorochrome bisbenzimide and direct observations on isolated sperm aster complexes show that halothane induces polyspermy (multiple sperm entry) when present at fertilization. Experimental evidence suggests that anesthetic-induced polyspermy involves impairment of both the fast (electrically mediated) and slow (morphological) blocks to multiple sperm entry. These observations clearly show that relatively brief exposures to halothane at fertilization cause polyspermy and that this effect is almost certainly responsible for the ensuing abnormal development observed at the first cell division.

Rapid visual detection of sperm-egg fusion using the DNA-specific fluorochrome Hoechst 33342.

When unfertilized sea urchin eggs are pretreated with the bisbenzimide DNA-specific fluorochrome Hoechst 33342, then washed and fertilized, a single sperm bound to the egg surface becomes intensely fluorescent. The location of the fluorescent sperm on the egg surface coincides exactly with the epicenter of the cortical reaction and the site at which the insemination cone subsequently appears. These observations, coupled with studies of eggs treated with quercetin to prevent fusion, as well as eggs made polyspermic by halothane exposure, indicate that the sperm acquires fluorescence as a consequence of fusion with the fluorochrome preloaded egg. Using a modification of this technique, we have found that cytoplasmic continuity between the sperm and egg is established at 4-8 sec after the onset of the sperm-induced conductance increase in the egg.

Induction of the acrosome reaction in sea urchin spermatozoa by the volatile anesthetic halothane.

The volatile anesthetic halothane rapidly and dose-dependently induces the acrosome reaction in sperm of the sea urchin Lytechinus variegatus. The reaction occurs equally well in artificial sea water containing 10 mM Ca2+ and in low (less than 100 microM)-Ca2+ media. The anesthetic-induced acrosome reaction can be prevented by pretreating sperm with EGTA, lanthanum, or procaine. In contrast, the Ca2+ channel blockers D-600, verapamil, diltiazem, and nitrendipene do not prevent the reaction. Acrosomal processes induced by halothane are ultrastructurally identical to those induced by egg jelly, the natural inducer of the acrosome reaction. These results suggest that Ca2+ in low quantity is required for the anesthetic-induced acrosome reaction and may be derived from internal sources. Enflurane, isoflurane, and methoxyflurane also induce the acrosome reaction, indicating that volatile anesthetics may be useful in studying ion changes accompanying sperm activation.

Comparative effects of halothane, enflurane, and methoxyflurane on the incidence of abnormal development using sea urchin gametes as an in vitro model system.

The incidence of sea urchin embryos developing abnormally after their exposure to equimolar concentrations of halothane, enflurane, and methoxyflurane has been determined. Halothane concentrations in the 0.6-1.25 mM range caused 18-96% of the embryos to undergo abnormal cleavage at the first cell division. This is important because embryos exhibiting atypical cleavage patterns at the first cell division eventually involute and die before reaching gastrulation. Over the same range of concentrations, enflurane and methoxyflurane have minimal effects on development. However, when exposed to 2.5 mM methoxyflurane, nearly 40% of the cells did not fertilize. These results show that volatile anesthetic agents have decidedly different effects on development and suggest that the incidence of abnormal development may not correlate directly with the anesthetic potency of inhalational agents.

Fentanyl does not inhibit fertilization or early development of sea urchin eggs.

Sea urchin (Lytechinus variegatus) eggs have been used to study the effects of fentanyl on in vitro fertilization and early development as a model of human in vitro fertilization. Fentanyl did not affect fertilization or subsequent cell division when present in concentrations calculated to approximate or exceed those to which human ora would be exposed during clinical anesthesia. Lytechinus eggs exposed to fentanyl, then washed in fentanyl-free sea water before fertilization were also not affected and divided normally. The results suggest potential clinical utility of fentanyl during the harvesting of human ova for subsequent in vitro fertilization.

Isolation of intact sperm asters from fertilized sea urchin eggs.

We have developed a procedure for isolating intact sperm asters in quantity from fertilized sea urchin eggs. This procedure is based on detergent-extraction methods developed previously for the bulk isolation of mitotic apparatuses. Using this protocol it is possible to isolate sperm asters as soon as they appear in the fertilized egg or at any subsequent point in their brief existence.

Isolation of microvillar microfilaments and associated transmembrane complex from ascites tumor cell microvilli.

The association of microvillar microfilaments with the microvillar membrane actin-containing transmembrane complex of MAT-C1 13762 ascites tumor cell microvilli has been investigated by differential centrifugation, gel electrophoresis and electron microscopy of detergent extracts of the isolated microvilli. Several methods have been used to reduce breakdown and solubilization of the microfilament core actin during the detergent extractions for preparation of microvillar core microfilaments. Gel electrophoresis of differential centrifugation fractions demonstrated that over 70% of the total microvillus actin could be pelleted with microfilament cores at 10 000 g under extraction conditions which reduce filament breakdown. Transmission electron microscopy (TEM) of all of the core preparations showed arrays of microfilaments and small microfilament bundles. The major protein components of the microfilament cores, observed by sodium dodecyl sulfate (SDS) electrophoresis, were actin and alpha-actinin. Among the less prominent polypeptide components was a 58 000 Dalton polypeptide (58 K), previously identified as a member of the MAT-Cl transmembrane complex. This three-component complex contains, in addition to 58 K, actin associated directly and stably with a cell surface glycoprotein (Carraway, CAC, Jung, G & Carraway, K L, Proc. natl acad. sci. US 80 (1983) 430). Evidence that the apparent association of complex with the microfilament core was not due simply to co-sedimentation was provided by myosin affinity precipitation. These results provide further evidence that the transmembrane complex is a site for the interaction of microfilaments with the microvillar plasma membrane.

Structural changes in dividing sea-urchin eggs induced by the volatile anaesthetic halothane.

Fertilized Lytechinus eggs exposed to the volatile anaesthetic halothane before metaphase do not undergo cytoplasmic cleavage. This effect has been correlated with the failure of the contractile ring to assemble. Comparative studies on mitotic apparatuses isolated from control and halothane-treated cells show that halothane significantly impairs both spindle and aster growth as early as metaphase. When transferred to control solutions, halothane-treated cells initiate furrowing activity in association with either the first or second mitotic division, depending on the duration of the exposure to anaesthetic and the concentration employed. In contrast to these effects, halothane has no effect on any aspect of the cleavage process if applied later than metaphase. In this case, furrows develop even in the presence of halothane, deepen progressively, and complete cell division. These observations confirm and extend previous studies on echinoderm eggs exposed to volatile anaesthetics, and support the view that anaesthetic agents indirectly prevent cell cleavage by inhibiting the growth of mitotic apparatus.

Macrotubules induced by halothane: in vitro assembly.

The formation of macrotubules by the volatile anaesthetic halothane was investigated in vitro using microtubule-enriched fractions of crayfish nerve cords. Sequential studies showed that macrotubules assemble from helical ribbons of 18-20 laterally associated microtubule protofilaments which fold upon themselves to form intact macrotubules averaging 48 nm in diameter. The initial rate of macrotubule assembly is dependent on the concentration of halothane employed and is stimulated by calcium. Glycerol pretreatment blocked macrotubule formation by halothane and caused preformed macrotubules to reassemble rapidly into typical microtubules. These experiments show that microtubules and macrotubules require different conditions for assembly and support the contention that macrotubule formation by halothane is due to a direct interaction between the anaesthetic molecule and the microtubule subunit.

Retrograde transport of horseradish peroxidase in the rat's brain during halothane anesthesia.

The horseradish peroxidase (HRP) method was used to study the effect of halothane anesthesia on retrograde transport in the central nervous system. Rats received neostriatal injections of 30% HRP (0.3 microl) and were placed in inhalation chambers perfused with air or air containing 1% halothane for up to 24 h. Subsequently, the brain were examined at rostro-caudal levels of the presence and distribution of HRP-containing cells. The number and distribution of HRP-labelled cells appearing at each cranial level were compared in control and halothane-anesthetized animals as a function of time. The results suggest that retrograde transport in the central nervous system is unaffected during halothane anesthesia.

Cultured neuroblastoma cells and halothane: effects on cell growth and macromolecular synthesis.

Cultured mouse neuroblastoma cells were grown in air-CO2 or air-CO2-halothane-gassed incubators. In the presence of halothane the growth rate of the cells was inhibited in a dose-dependent manner; 2 per cent halothane completely inhibited cell growth, while at 0.3 per cent halothane, the growth rate was 74 per cent of the control rate. The biosynthesis of protein and RNA in cells grown in the control atmosphere and that in cells grown in 1 per cent halothane were compared by several techniques. No significant difference between the rates of synthesis of these two macromolecules could be detected. Furthermore, a comparison of labeled protein and RNA by SDS-polyacrylamide gel electrophoresis revealed no qualitative difference. From this and previous work it is concluded that halothane affects the morphology and growth rate of cultured mouse neuroblastoma cells by disrupting cytoplasmic actin-like micro-filaments.