The looming retirement crisis

A retirement crisis looms in the United States due to a number of recent and emerging trends that affect government retirement programs, employer- and union-sponsored retirement benefits and personal savings arrangements. The crisis can be averted, but only with well-thought-out action on a number of issues, particularly Social Security and Medicare reform.

Establishing a normal range for mouth opening: its use in screening for oral submucous fibrosis

The maximal mouth opening of 700 healthy Nepalese adults, age range of 18-68 years, measured by paraclinical workers was determined as there are no data available for an Asian population. The mean value of the inter-incisal distance was 47.1 mm (range 33.7-60.4 mm) and 98% of the population surveyed fell within this range. The minimum limit of normal oral opening was determined to be 34 mm. Ten out of 13 patients with histologically confirmed oral submucous fibrosis (OSF) had a maximal oral opening of less than 34 mm. It was concluded that reduced oral opening measured by paraclinical workers as a single screening test for oral submucous fibrosis, has a sensitivity of only 77% and will detect only advanced cases. However, each of the 3 subjects from the healthy population found to have restricted mandibular opening and who agreed to be examined further had significant oral conditions, namely oral submucous fibrosis (2) and pericoronitis (1). The study confirms the value of this measurement as a screening procedure for significant oral disease by paraclinical staff particularly in developing countries where trained dental and medical personnel are scarce. Because of its limited sensitivity, measurement of mouth opening is unsatisfactory as a single screening test for OSF, as it will not detect early stages of the disease.

Interactions with the pharmaceutical industry: a survey of family medicine residents in Ontario

OBJECTIVE

To determine the attitudes, knowledge and practices of family medicine residents relating to the pharmaceutical industry and to assess the effectiveness of existing guidelines on appropriate interactions with the pharmaceutical industry.

DESIGN

Survey by mailed questionnaire.

SETTING

Ontario.

PARTICIPANTS

All 262 second-year family medicine residents in Ontario (seven centres); 226 (86.3%) responded.

RESULTS

Fifty-two (23.0%) of the residents who responded stated that they had read the CMA policy statement on appropriate interactions between physicians and the pharmaceutical industry. A total of 124 (54.9%) stated that they would attend a private dinner paid for by a pharmaceutical representative; the proportion was not significantly reduced among those who had read the CMA guidelines, which prohibit the acceptance of personal gifts. In all, 186 (82.3%) reported that they would like the opportunity to interact with pharmaceutical representatives in an educational setting, even though several programs now discourage these interactions. Approximately three quarters (172/226 [76.1%]) of the residents indicated that they plan to see pharmaceutical representatives in their future practice. Residents at Centre 2 were significantly more critical of the pharmaceutical industry than those from the other centres. Overall, being aware of, and familiar with, departmental policy or CMA policy on interactions with the pharmaceutical industry did not affect the residents' attitudes or intended future practices.

CONCLUSION

The presence of guidelines concerning physicians' interactions with the pharmaceutical industry does not appear to have a significant impact on family medicine residents in Ontario.

Oral submucous fibrosis. A review

Oral submucous fibrosis (OSF) affects an estimated 2.5 million people, mostly in the Indian subcontinent. Limitation of oral opening resulting in difficulty in eating is the main presenting feature. Although nutritional deficiencies and immunological processes may play a part in the pathogenesis, the available epidemiological evidence indicates that chewing betel quid (containing areca nut, tobacco, slaked lime or other species) is an important risk factor for OSF. Genetically determined susceptibility could explain why only a small fraction of those using betel quid develop the disease. In OSF there is an incidence of oral cancer of 7.6 per cent for a median 10-year follow-up period. Risk markers for malignant transformation in OSF include epithelial dysplasia, silver binding nucleolar organizer region counts, and sister-chromatid exchange frequencies; p53 tumour suppressor gene mutations may be involved in these potentially malignant changes.

Reproductive characteristics of a population of urban Swiss women

OBJECTIVE

To describe the variability of reproductive life, from menarche to menopause, in the Geneva female population.

DESIGN

Women's Health Survey, 1992-1993.

SETTING

Mobile epidemiology unit of a University Hospital.

SUBJECTS

One thousand and thirty-two women aged 30 to 74 years, resident in Geneva, Switzerland.

MAIN OUTCOME MEASURE

Menstrual and reproductive history.

RESULTS

A 'typical' woman of Geneva has her menarche at 13 years, regular 28 day cycles with 5 days of menstrual flow. She is 26 years old when she first gives birth and has her last baby (which is typically the second) at age 31. She has 37 years of potential fecundity and a natural menopause at age 50. In addition, 11% of the women have tried to be pregnant during two years without success, 67% have ever used oral contraceptives, 20% had a first birth at age 30 or more and 23% were nulliparous. Younger women reported earlier ages at menarche. Women with lower education tended to be a younger age at the birth of her first child.

CONCLUSIONS

In this first study of the reproductive characteristics of women in Geneva, nulliparity and a late first birth appeared unusually frequent, especially when compared with American or Chinese women. The observed distributions of reproductive history are compatible with the very high incidence rate of breast cancer in the Geneva population.

Epithelial growth fraction and expression of p53 tumour suppressor gene in oral submucous fibrosis

The incidence of squamous cell carcinoma in patients with oral submucous fibrosis (OSF) exceeds 7 per cent. The proliferative cell nuclear antigen (PCNA) is a convenient marker of epithelial cell proliferation and p53 tumour suppressor gene mutations or deletions are frequent in oral cancer. The present study estimated the basal epithelial cell growth fraction using a standard immunohistological method for the detection of nuclear PCNA from 20 Nepalese patients with OSF as 31.8 per cent compared with 7.6 per cent for oral mucosa from 43 normal subjects (p < 0.001) and 39.4 per cent for 44 patients with oral cancer. The PCNA growth fraction correlated significantly with that derived by Ki-67 labelling. There was no correlation between the growth fraction and the severity of epithelial dysplasia found is OSF. Abnormal expression of p53 protein identified by immunohistochemistry with a panel of antibodies was found in 70 per cent of the OSF specimens, and 21 per cent of mucosal specimens from subjects with clinically normal mouths. PCNA-positive cells and p53 expression were restricted to the basal epithelial layer in OSF. The unexpected finding of p53 protein in clinically healthy mucosa was confined to subjects aged over 40 years who smoked tobacco, a known risk factor for oral cancer. There was no association between p53 expression and epithelial atypia scores in OSF. It is concluded that the proportion of actively cycling epithelial cells is increased in OSF and that p53 tumour suppressor gene mutations or deletions may be prevalent. Confirmation by molecular biology techniques of this genetic damage is now needed.

Seroepidemiology of herpes virus infections among dental personnel

OBJECTIVES

To examine the possible occupational hazard of infection with human herpes viruses among dental personnel.

METHODS

Sera from 81 preclinical dental students, 53 clinical dental students and 103 qualified dental surgeons were tested for antibodies to herpes simplex virus type 1 (HSV-1), cytomegalovirus (CMV), Epstein-Barr virus (EBV) and human herpes virus type 6 (HHV-6). The same number of control subjects, matched individually for age (+/- 1 year), sex and social class, was also examined. Antibodies were detected by ELISA for HSV-1, latex agglutination for CMV, indirect immunofluorescence with P3HR1 cells for EBV and indirect immunofluorescence with infected JJhan cells for HHV-6. Each participant also completed a questionnaire to permit correlation of demographic data and risk factors with serological results.

RESULTS

No significant difference in seroprevalence was detected between any of the dental groups and their respective controls. There was a significantly higher prevalence of antibodies to EBV among clinical students (P = 0.02) and qualified dentists (P = 0.0003) than among preclinical students. These significant increases were not mirrored in the three corresponding control groups.

CONCLUSION

The results suggest a possible occupational risk of infection with EBV in dentists. There was no evidence for a significant risk of occupational infection with HSV-1, CMV or HHV-6.

Intranuclear post-transcriptional down-regulation responsible for loss of a keratin differentiation marker in tumour progression

Apparent loss of differentiation markers characterizes advanced malignant neoplasms. Post-transcriptional down-regulation of keratin message to levels undetectable with a partial cDNA probe to rat keratin K5 had been observed in anaplastic cells (T952/F7) derived from benign keratin-producing cells (A5P/B10) (1). The entire fifth introns of both the K5 and K6 genes were generated from rat genomic DNA by PCR to define expression of these closely related proteins. Sequencing of the PCR products revealed 84% homology in the K5 and K6 exon regions included, but absence of any homology in the introns. Active transcription of K5 could be demonstrated in the anaplastic cells with reverse transcription of nuclear RNA (RTn-PCR) by the presence of PCR-generated products confirmed by sequencing as unspliced and spliced transcripts of rat K5. In situ hybridization with ssDNA probes for the spliced message from this region of the K5 gene demonstrated a punctuate distribution in the cytoplasm of the benign cells and absence of any detectable message in the anaplastic derivatives, ssDNA probes for the unspliced transcript containing intron 5 and the same flanking exon sequences as the spliced probe detected transcription of hnRNA in the anaplastic cells as discrete signals confined to the nuclear compartment. These results show that failure to express mRNA for a differentiation marker in the cytoplasm of anaplastic cells can be due to a mechanism operating in the nuclear compartment after gene transcription and indicate that the mechanism functions shortly after splicing of the transcript.

Structure-activity relationships of the potent combined endothelin-A/endothelin-B receptor antagonist Ac-DDip16-Leu-Asp-Ile-Ile-Trp21: development of endothelin-B receptor selective antagonists

The endothelins (ETs) are a family of bicyclic 21-amino acid-containing peptides that are highly potent and prolonged vasoconstrictors. The discovery of potent ET antagonists will facilitate the understanding of the physiological and/or pathophysiological role of ET. Structure-activity studies have revealed the importance of the C-terminal hexapeptide (residues 16-21) of ET (His16-Leu17-Asp18-Ile19-Ile20-Trp21) to the development of potent antagonists at both receptor subtypes (ETA and ETB). In particular, it has been shown that Ac-DDip16-Leu-Asp-Ile-Ile-Trp21 (Dip = 3,3-diphenylalanine) has low nanomolar affinity for the two endothelin receptor subtypes and is a functional antagonist of ET activity, both in vitro and in vivo at both receptors. Herein, we will describe the structure-activity relationships of Ac-DDip16-Leu-Asp-Ile-Ile-Trp21 (PD 142893) with a particular emphasis on modifications that lead to enhanced receptor affinity and/or individual receptor subtype selectivity. In particular, we will demonstrate how we utilized PD 142893 to develop ETB receptor selective ligands and the pharmacological differences that exist between species ETB receptors with respect to their affinity for C-terminal hexapeptide antagonists.

Preconditioning in isolated superfused human muscle

Studies in isolated superfused rabbit papillary muscles indicate that preconditioning (PC) is not confined to arterially perfused myocardium. In the present study PC of isolated human right atrial trabeculae was investigated avoiding the problems of invasive experimentation in patients. Atrial trabeculae were suspended in an organ bath, superfused with Tyrode's solution and field stimulated at 1 Hz. After stabilization, muscles were randomly allocated to five groups (n = 8 per group). Control (C) muscles had no additional treatment. PC was induced by 3 min rapid pacing at 3 Hz with hypoxic substrate-free buffer, followed by reoxygenation with substrate for 12 min. In two additional groups 8-p-sulfophenyltheophylline (SPT) was added to the superfusate either during stabilization in controls (C+SPT) or during preconditioning (PC+SPT). In the final group, R-phenyl-isopropyl adenosine (R-PIA) was added to the superfusate for 5 min to see whether or not this could substitute for preconditioning. All muscles were then exposed to 90 min hypoxia with no substrate and pacing at 3 Hz, followed by 120 min reoxygenation at 1 Hz. Recovery of developed tension was significantly improved by PC 46.5 +/- 2.4% v 24.6 +/- 2.3% in controls) and this protective effect was blocked by the addition of SPT without adversely affecting controls (recovery in PC+SPT, 25.8 +/- 4.1% and C+SPT, 22.7 +/- 2.9%). R-PIA protected the muscles to a similar extent as PC (43.8 +/- 1.9%). These data provide evidence for the involvement of adenosine in preconditioning in human myocardium.

Pharmacological characterization of PD 156707, an orally active ETA receptor antagonist

We describe the pharmacological characteristics of PD 156707 (sodium 2-benzo[1,3]dioxol-5-yl-4-(4-methoxy-phenyl)-4-oxo-3-(3,4,5- trimethoxy-benzyl)-but-2-enoate), a potent, orally active, nonpeptide antagonist of the endothelin A (ETA) receptor subtype. PD 156707 was designed on the basis of a compound identified by screening the Parke-Davis chemical library. PD 156707 is highly selective for the ETA receptor (ETAR) and inhibits the binding of [125I]-ET-1 to cloned human ETAR and ETBR with Ki values of 0.17 and 133.8 nM, respectively. PD 156707 antagonizes ET-1-stimulated phosphoinositide hydrolysis in Ltk- cells expressing cloned human ETAR with an IC50 value of 2.4 nM. PD 156707 inhibits vasoconstriction in isolated blood vessels mediated by ETAR (rabbit femoral artery) and ETBR (rabbit pulmonary artery) with pA2 values of 7.5 and 4.7, respectively. PD 156707 administered orally to rats blocked subsequent ETAR-mediated pressor responses in vivo but had no effect on ETBR-mediated dilator responses. As a potent and orally active ETA-selective antagonist, PD 156707 will be useful in defining the physiological and pathological roles of ETAR.

The cytoplasmic domain of L-selectin interacts with cytoskeletal proteins via alpha-actinin: receptor positioning in microvilli does not require interaction with alpha-actinin

The leukocyte adhesion molecule L-selectin mediates binding to lymph node high endothelial venules (HEV) and contributes to leukocyte rolling on endothelium at sites of inflammation. Previously, it was shown that truncation of the L-selectin cytoplasmic tail by 11 amino acids abolished binding to lymph node HEV and leukocyte rolling in vivo, but the molecular basis for that observation was not determined. This study examined potential interactions between L-selectin and cytoskeletal proteins. We found that the cytoplasmic domain of L-selectin interacts directly with the cytoplasmic actin-binding protein alpha-actinin and forms a complex with vinculin and possibly talin. Solid phase binding assays using the full-length L-selectin cytoplasmic domain bound to microtiter wells demonstrated direct, specific, and saturable binding of purified alpha-actinin to L-selectin (Kd = 550 nM), but no direct binding of purified talin or vinculin. Interestingly, talin potentiated binding of alpha-actinin to the L-selectin cytoplasmic domain peptide despite the fact that direct binding of talin to L-selectin could not be measured. Vinculin binding to the L-selectin cytoplasmic domain peptide was detectable only in the presence of alpha-actinin. L-selectin coprecipitated with a complex of cytoskeletal proteins including alpha-actinin and vinculin from cells transfected with L-selectin, consistent with the possibility that alpha-actinin binds directly to L-selectin and that vinculin associates by binding to alpha-actinin in vivo to link actin filaments to the L-selectin cytoplasmic domain. In contrast, a deletion mutant of L-selectin lacking the COOH-terminal 11 amino acids of the cytoplasmic domain failed to coprecipitate with alpha-actinin or vinculin. Surprisingly, this mutant L-selectin localized normally to the microvillar projections on the cell surface. These data suggest that the COOH-terminal 11 amino acids of the L-selectin cytoplasmic domain are required for mediating interactions with the actin cytoskeleton via a complex of alpha-actinin and vinculin, but that this portion of the cytoplasmic domain is not necessary for proper localization of L-selectin on the cell surface. Correct L-selectin receptor positioning is therefore insufficient for leukocyte adhesion mediated by L-selectin, suggesting that this adhesion may also require direct interactions with the cytoskeleton.

Increased mortality from inadequate provision of coronary care unit facilities

Over a 6-month period, all patients admitted to the Royal United Hospital, Bath, with acute ischaemic heart disease were prospectively followed for the period of their hospital stay. Strict admission and discharge criteria were defined for the Coronary Care Unit (CCU), so that groups of patients could be identified in which the treatment was not ideal. The mortality in the groups of patients who were admitted to the CCU without delay and for an appropriate length of time was 5.1% (18/355). It was significantly higher overall in the groups of patients who were either not admitted (14.3%, 4/28) or whose admission was delayed (17.4%, 4/23). The results underline the importance of the provision of adequate coronary care facilities.

Preconditioning in isolated superfused rabbit papillary muscles

Preconditioning has only been demonstrated in arterially perfused myocardium. Our aim was to develop a model of preconditioning in isolated, superfused, isometrically contracting rabbit right ventricular papillary muscle. This would eventually allow us to evaluate isolated human muscles. Papillary muscles were suspended in an organ bath, superfused with oxygenated Tyrode solution, and field stimulated at 1 Hz. Muscles were assigned either to control or to preconditioning groups. Preconditioning was induced with 3 min of rapid pacing (3 Hz) with substrate-free hypoxic buffer and was followed by 15 min of reoxygenation with substrate. Subsequently, both groups were exposed to 45 min of substrate-free hypoxia followed by 120 min of reoxygenation with substrate. Preconditioning protected the myocardium with better recovery of developed force (50.6 +/- 6.7 vs. 27.4 +/- 4.2% of baseline developed force, P < 0.01). This effect could be blocked by 8-(p-sulfophenyl)theophylline (SPT) given during preconditioning at a dose that did not increase hypoxic damage in controls (percent developed force compared to baseline: preconditioned muscles + SPT = 30.9 +/- 2.8% and control muscles + SPT = 27.1 +/- 2.3%). In addition, pretreatment with (-)N6(2-phenylisopropyl)adenosine similarly protected the myocardium (49.5 +/- 5.5% recovery, P < 0.01). We conclude that isolated superfused muscles can be preconditioned. This preconditioning does not depend on coronary flow and involves activation of adenosine receptors.

Global myocardial ischemia protects the myocardium from subsequent regional ischemia

Many investigators use in vitro models of global ischemia to examine the effects of preconditioning, often with recovery of contractile function as the end-point. Such models are relevant to myocardial protection during cardiac surgery. However, there is still debate as to whether preconditioning preserves ventricular contraction secondary to limitation of infarction or by a direct effect on stunning. Since infarct size is the original end-point against which protection by preconditioning is measured, our aims were, first, to validate global ischemic preconditioning by measuring infarct size after subsequent regional ischemia and, second, to correlate limitation of infarct size with mechanical function. After stabilization, seven isolated buffer perfused rabbit hearts were subjected to 5 minutes of global "no-flow" ischemia followed by 10 minutes of reperfusion ("global preconditioning"). Seven control hearts were allowed to stabilize for an additional 15 minutes at constant flow. Subsequently, regional ischemia was induced in both groups for 45 minutes followed by 2 hours of reperfusion. Left ventricular and coronary perfusion pressures were measured throughout. Myocardial infarct size was measured using triphenyltetrazolium staining and expressed as a percentage of the area at risk outlined with fluorescent microspheres. The ratio of infarct to risk zone was reduced from 47.6 +/- 7.3% in control hearts to 16.4 +/- 5.4% (p = 0.005) in preconditioned hearts, confirming the efficacy of global preconditioning. In addition, preconditioning led to a better preservation of systolic function, which correlated significantly with limitation of infarct size (r = 0.75, p = 0.002). Global preconditioning may account for the successful use of cross-clamp fibrillation during cardiac surgery.

A clinical trial of prostaglandin E2 in recurrent aphthous ulceration

Thirty-five patients suffering from minor recurrent aphthous ulceration (RAU) entered a single-phase double-blind clinical trial of treatment with topical prostaglandin E2 (PGE2). The PGE2 was applied as a gel at a dose of 0.3 mg twice daily for 10 days. The vehicle alone acted as control. Patients were examined on days 1, 3, 5, 7 and 10 and also maintained daily diary cards. Of the 33 patients (94%) who completed the study, 18 had been allocated the active PGE2 and 15 the placebo. The two volunteers who failed to complete were excluded on technical grounds related to the strict study design and did not withdraw on the basis of adverse reactions to the trial preparation. Patients using the active PGE2 gel experienced significantly fewer new lesions than those on placebo (P < 0.05) over the 10-day trial period. There were no significant differences between the PGE2 and placebo gels in terms of speed of healing or pain relief of established aphthous ulcers. Prostaglandin E2 may, therefore, have useful prophylactic activity in RAU.

Heat stress limits infarct size in the isolated perfused rabbit heart

OBJECTIVE

Heat stress, with the expression of heat stress proteins, has been shown to protect the rabbit heart in vitro against global ischaemia/reperfusion injury, though no benefit is apparent in an in vivo rabbit model of infarct size. The aim of this study was therefore to investigate this discrepancy and to discover whether heating itself has any effect which could negate the protection derived from myocardial stress protein synthesis.

METHODS

(1) To ascertain whether heat stress could limit infarct size in the absence of blood, isolated buffer perfused hearts, with or without prior heat stress, were subjected to 45 min of regional ischaemia and 120 min reperfusion, and the resulting infarct size was expressed as a percentage of the risk area (I/R%). (2) The observations were repeated in an isolated blood perfused heart model in which a support rabbit (heat stressed or control) was used to perfuse the isolated heart.

RESULTS

In the buffer perfused heart, prior heat stress reduced I/R from 70.8(SEM 4.4)%, n = 10, in controls to 51.5(5.7)%, n = 12 (p < 0.05). In hearts perfused by support rabbits, prior heat stress reduced I/R [from 34.7(3.7)%, n = 16, to 23.5(3.3)%, n = 15 (p < 0.05)] only when the perfusing rabbit was a control (not heat stressed). If the perfusing rabbit had been heated, I/R was greater in both heat stressed and control hearts [51.9(7.0)% and 44.9(3.3)%, p < 0.05 v control support rabbit].

CONCLUSIONS

Heat stress limits infarct size in this rabbit model. However it appears to have additional adverse effects, probably on the blood, which may override any benefit associated with myocardial stress protein synthesis.

A single five minute period of rapid atrial pacing fails to limit infarct size in the in situ rabbit heart

OBJECTIVE

Rapid pacing has been shown to precondition the dog heart against ischaemic dysrhythmia. The aim of this study was to determine whether rapid pacing could also limit infarct size.

METHODS

Rabbits (n = 5) were rapidly paced via the left atrium at 420-480 beats.min-1. Five min of rapid pacing and 10 min of recovery in sinus rhythm were followed by 45 min of regional ischaemia and 120 min of reperfusion. Control rabbits (n = 9) were treated identically without prior rapid pacing. Infarct size was determined in both groups using tetrazolium and expressed as a percentage of the area at risk demarcated by fluorescent microspheres. In a separate series of experiments, rapidly paced Langendorff perfused rabbit hearts (n = 9) were used to determine coronary flow under perfusion conditions designed to simulate the in vivo situation during rapid pacing.

RESULTS

Rapid pacing caused a fall in systolic pressure from 91.4(SEM 4.5) to 47.0(5.9) mm Hg (p < 0.01) and diastolic pressure from 67.2(2.9) to 23.6(3.2) mm Hg (p < 0.01). Both recovered within 30 s of cessation of pacing. During rapid pacing the action potential duration shortened from 192(13) to 128(5) ms (p = 0.01) and developed electrical alternans (n = 4). Following rapid pacing the ECG showed either ST depression or T wave inversion (n = 4). Despite these profound changes, rapid pacing did not reduce infarct size v control [52.7(4.6)% v 60.8(9.1)% of the area at risk, respectively]. The in vitro experiments estimated that rapid pacing would result in a reduction in coronary flow to 44% of that in sinus rhythm without a significant rise in lactate efflux.

CONCLUSIONS

In our model, pretreatment with rapid pacing fails to reduce infarct size. The most likely reason for this is that rapid pacing at a rate of 480 beats.min-1 does not cause myocardial ischaemia of sufficient severity to trigger the preconditioning response.

Haemolysis following mitral valve repair

We report the unusual occurrence of severe intra-vascular haemolysis following mitral valve repair. Mild to moderate mitral regurgitation was detected after repair, but severe haemolysis was the only indication for re-operation. Following prosthetic valve replacement there was an immediate cessation of haemolysis. We postulate that a small regurgitant jet directed against the teflon pledgets used in the repair was the reason for the haemolysis.

Salivary IgA antigliadin antibody as a marker for coeliac disease

In recent years, serum antibodies to gliadin (AGA) have been reported to be useful markers of coeliac disease. IgA AGA have also been found in intestinal secretions and saliva in coeliac disease and may offer a convenient, non-invasive screening test. In order to test this hypothesis, salivary and serum AGA were measured in children with coeliac disease proved by biopsy and compared with several control groups. Measurement of salivary IgA AGA provided excellent discrimination between those children with coeliac disease and the control groups, and our study suggests that it may provide a rapid, non-invasive method of screening for this disease before intestinal biopsy.

The origins of the human immunodeficiency viruses: an update

In 1981 a new acquired immunodeficiency syndrome was first described. The disease has a 100% mortality rate and over 359,000 cases have been reported to the WHO from 162 countries. The WHO estimates that the cumulative global total of AIDS cases as of early 1991 is more than 1.5 million. The dental profession, in line with other health care professions, is involved with guiding rational efforts to stop transmission and with developing effective means of treatment and prevention. This paper reviews the nature of the virus, its possible origins, and the implications of such origins for treatment and prevention of the disease.