A new "cool" lens capsulotomy laser

A new infrared "cool" laser has been developed to facilitate extracapsular cataract extraction. It has been used to produce clinically and histologically safe, effective anterior and posterior capsulotomies in animal studies. This newly developed ophthalmic laser system operates at a wavelength of 1220 nm, and has a maximal retinal absorption of only 0.1%. This is 100 times less than the retinal absorption at the wavelength of the neodymium-YAG laser. Retinal safety is not dependent on the creation of a plasma shield or on mechanical safety devices, as it is for the neodymium-YAG laser. The 1220 nm wavelength also enhances the "cool laser" effect, so that only 1/100 of the power intensity of the modelocked neodymium-YAG laser is required. In addition to lowering the required ocular exposure this may reduce the likelihood of intraocular damage. To our knowledge this represents the first intraocular use of a laser at this wavelength region (1200 to 1290 nm). A second generation laser, using erbium yttrium lithium fluoride (YLF) as its lasing medium, is currently being developed.

Steps toward resolving cultural conflict in a pediatric hospital

A serious and potentially life-threatening disease in a young child was identified and resolved through medical intervention. However, in the course of hospitalization, a conflict arose between the mother and the health care providers that required legal constraints on the mother. A retrospective account of this conflict between Western health care providers and a family from a Caribbean culture lends itself to an examination of the role of cultural considerations in pediatric hospital care. Suggestions for resolving cultural conflict in clinical practice are discussed.

Mechanistic studies on the pyridoxal phosphate enzyme 1-aminocyclopropane-1-carboxylate deaminase from Pseudomonas sp

The enzyme 1-aminocyclopropane-1-carboxylate deaminase (ACPC deaminase) from a pseudomonad is a pyridoxal phosphate (PLP) linked catalyst which fragments the cyclopropane substrate to alpha-ketobutyrate and ammonia [Honma, M., & Shimomura, T. (1978) Agric. Biol. Chem. 42, 1825]. Enzymatic incubations in D2O yield alpha-ketobutyrate with one deuterium at the C-4 methyl group and one deuterium at one of the C-3 prochiral methylene hydrogens. Stereochemical analysis of the location of the C-3 deuteron was accomplished by in situ enzymatic reduction to (2S)-2-hydroxybutyrate with L-lactate dehydrogenase and conversion to the phenacyl ester. The C-3 hydrogens of the (2S)-2-hydroxybutyryl moiety are fully resolved in a 250-MHz NMR spectrum. Absolute assignment of 3S and 3R loci was obtained with phenacyl (2S,3S)-2-hydroxy[3-2H]butyrate generated enzymatically by D-serine dehydratase action on D-threonine. ACPC deaminase shows a stereoselective outcome with a 3R:3S deuterated product ratio of 72:28. 2-Vinyl-ACPC is also a fragmentation substrate with exclusive regiospecific cleavage to yield the straight-chain keto acid product 2-keto-5-hexenoate. The D isomer of vinylglycine is processed to alpha-ketobutyrate and ammonia at 8% the Vmax of ACPC, while L-vinylglycine is not a substrate. It is likely that ACPC and D-vinylglycine yield a common intermediate--the vinylglycine-PLP-p-quinoid adduct--which is then protonated sequentially at C-4 and then C-3 to account for the observed deuterium incorporation. The D isomers of beta-substituted alanines (fluoroalanine, chloroalanine, and O-acetyl-D-serine) partition between catalytic elimination and enzyme inactivation. Each shows a different partition ratio, arguing against the common aminoacrylyl-PLP as the inactivating species.

Mechanistic studies on reactions of bacterial methionine gamma-lyase with olefinic amino acids

Methionine gamma-lyase (EC 4.4.1.11), which catalyzes the formation of methanethiol, alpha-ketobutyrate, and ammonia from L-methionine (eq 1), promotes the oxidative deamination of several four- and five-carbon olefinic amino acids (1-5). With the exception of vinylglycine (1), the Vmax rates of keto acid formation from the unsaturated substrate analogues are substantially lower than that for processing of methionine to alpha-ketobutyrate; vinylglycine is deaminated to ketobutyrate and ammonia with a Vmax twice that for L-methionine turnover. L-Allylglycine, L-2-amino-3-trans-pentenoate, and L-2-amino-3-cis-pentenoate (2, 4, 5) are all converted to 2-keto-pentanoic acid (alpha-ketovalerate). L-2-Amino-3-cis-pentenoate (5) is also a time-dependent, irreversible inactivator of the enzyme. None of the other substrate analogues tested appears to inactivate the enzyme. Spectral analysis of the enzymatic reaction with cis isomer 5 reveals the formation of a high-wavelength chromophore (lambda max = 550 nm ) which implies that a beta, gamma-unsaturated pyridoxal p-quinoid (VI) accumulates. No such absorbing species appears to form during the reaction of trans isomer 4 with methionine gamma-lyase. But a 550-nm chromophore develops when both 4 and 5 are reacted with Al(NO3)3 and pyridoxal methochloride in methanolic KOH. It would appear that the geometry of the protein and the olefinic amino acid as an intermediate enzyme-substrate adduct controls the kinetics of reaction, such that azaallylic isomerization becomes selectively rate determining for reaction with 5. When this isomerization is slow, an accumulating Michael-type acceptor (VI) could lead to the observed irreversible inactivation of the enzyme.

The pharmacodynamics of bucainide (RHC G233): pharmacokinetic parameters and relationship between plasma levels and the effect on the electrocardiogram in the dog

The pharmacodynamic profile of bucainide dimaleate (RHC G-233) in dogs has been studied. The first observed pharmacologic effect was a change in the ECG pattern (T-wave duration and amplitude) that occurred after an average intravenous dose of 2.7 mg/kg. The average plasma concentration of bucainide was approximately 350 ng/ml. Analysis of data from dogs that received a dual infusion of bucainide indicated that bucainide has an extensive volume of distribution, with an average value of approximately 26 l/kg. An average terminal half-life of 89 minutes was observed. Studies with the radiolabeled drug in rats and dogs also demonstrated the drug's large volume of distribution, and its initial rapid disappearance from the blood. Tissue distribution studies in the rat after administration of the radiolabeled drug showed that bucainide is rapidly taken up by the tissues.

Effect of maternal cigarette smoking on Apgar scores

As shown in a total of 43,492 live-born singleton infants, the proportion of low and depressed Apgar scores is related to the extent of maternal cigarette usage during pregnancy. In particular, the three-pack level of smoking (41 to 60 cigarettes per day) is reflected in a near-quadrupling of low and depressed one-minute and five-minute Apgar scores in both blacks and whites and also after exclusion of prematurely born infants.

Relationship between pre-operative anxiety and post-operative state

Janis (1958) has proposed a curvilinear relationship pre-operative anxiety and post-operative emotional state. While other hypotheses share the prediction of a poor outcome for patients with pre-operative high anxiety, Janis' theory is unique in predicting a poor outcome for those with low anxiety. Subsequent research has failed to confirm Janis' hypotheses, perhaps because the designs have been insensitive to the predictions for low anxiety patients. The current study tests the hypothesis more directly and finds some support for a linear relationship between pre-operative anxiety and post-operative negative affect, with no support for Janis' curvilinear hypothesis. On the whole, pre-operative anxiety was a poor predictor of other measures of recovery but, on one measure, patients with low anxiety showed a slower recovery than those with moderate anxiety, i.e. supporting the prediction of a poor outcome for low anxiety patients. The implications of these results for pre-operative preparation of surgical patients and the development of theories of anxiety are discussed.

Anxiety in surgical patients

The natural course of anxiety before and after surgery was examined using the State-Trait Anxiety Inventory in 4 studies involving 136 surgical patients. The results suggested that high levels of anxiety were experienced before admission to hospital, between admission and surgery and following surgery, and were not restricted to the immediate pre-operative period. Only a small percentage of patients reached their maximum level of anxiety on the morning of surgery. These results have implications for those planning interventions to alleviate anxiety associated with surgery and for those studying surgical stress as a model for other naturally occurring stresses.

Cultural variations in professional and parenting patterns

Existing parental and professional caring patterns are explored in an attempt to lay a foundation for the development of culturally relevant perinatal programs. Beliefs about bonding behavior are discussed as well as exploring whether this new knowledge is consistent with cross-cultural adaptations to the birth process. New rules and customs being introduced by professionals may be fostering a "detachment" phenomenon rather than the desired result of bonding behavior between parent and infant. Finally, a method of examining culturally divergent health beliefs and practices is discussed as a means of evaluating whether such practices are likely to be beneficial or harmful.

Suicide inactivation of bacterial cystathionine gamma-synthase and methionine gamma-lyase during processing of L-propargylglycine

L-Propargylglycine, a naturally occurring gamma, delta-acetylenic alpha-amino acid, induces mechanism-based inactivation of two pyridoxal phosphate dependent enzymes of methionine metabolism: (1) cystathionine gamma-synthease, which catalyzes a gamma-replacement reaction in methionine biosynthesis, and (2) methionine gamma-lyase, which catalyzes a gamma-elimination reaction in methionine breakdown. Biphasic pseudo-first-order inactivation kinetics were observed for both enzymes. Complete inactivation is achieved with a minimum molar ratio ([propargylglycine]/[enzyme monomer]) of 4:1 for cystathionine gamma-synthase and of 8:1 for methionine gamma-lyase, consistent with a small number of turnovers per inactivation event. Partitioning ratios were determined directly from observed primary kinetic isotope effects. [alpha-2H]Propargylglycine displays kH/kD values of about 3 on inactivation half-times. [alpha-3H]-Propargylglycine gives release of tritium to solvent nominally stoichiometric with inactivation but, on correction for the calculated tritium isotope discrimination, partition ratios of four and six turnovers per monomer inactivated are indicated for cystathionine gamma-synthase and methionine gamma-lyase, respectively. The inactivation stoichiometry, using [alpha-14C]-propargylglycine, is four labels per tetramer of cystathionine gamma-synthase but usually only two labels per tetramer of methionine gamma-lyase (half-of-the-sites reactivity). Two-dimensional urea isoelectrofocusing/NaDodSO4 electrophoresis suggests (1) that both native enzymes are alpha 2 beta 2 tetramers where the subunits are distinguishable by charge but not by size and (2) that, while each subunit of a cystathionine gamma-synthase tetramer becomes modified by propargylglycine, only one alpha and one beta subunit may be labeled in an inactive alpha 2 beta 2 tetramer of methionine gamma-lyase. Steady-state spectroscopic analyses during inactivation indicated that modified cystathionine gamma-synthase may reprotonate C2 of the enzyme--inactivator adduct, so that the cofactor is still in the pyridoxaldimine oxidation state. Fully inactivated methionine gamma-lyase has lambda max values at 460 and 495 nm, which may represent conjugated pyridoximine paraquinoid that does not reprotonate at C2 of the bound adduct. Either species could arise from Michael-type addition of an enzymic nucleophile to an electrophilic 3,4-allenic paraquinoid intermediate, generated initially by propargylic rearrangement upon a 4,5-acetylenic pyridoximine structure, as originally proposed for propargylglycine inactivation of gamma-cystathionase [Abeles, R., & Walsh, C. (1973) J. Am. Chem. Soc. 95, 6124]. It is reasonable that cystathionine gamma-synthase is the major in vivo target for this natural acetylenic toxin, the growth-inhibitory effects of which are reversed by methionine.

Insider-out: the health worker as researcher

This article discusses two dimensions related to the insider-outsider dilemma in conducting anthropological research in the health setting. One dimension concerns advantages of the insider's special knowledge in selecting and conducting successful research in a health institution. The other dimension deals with the ambiguity and confusion of roles attributed by staff to the investigator who may be seen as practitioner as well as social scientist. The patient may also see the researcher as performing dual, and possibly conflicting, roles. The advantage gained in the first dimension may be negated, to some extent, by the disadvantages associated with the second.

Mechanistic studies with vinylglycine and beta-haloaminobutyrates as substrates for cystathionine gamma-synthetase from Salmonella typhimurium

Cystathionine gamma-synthetase (EC 4.2.99.9), a key enzyme in bacterial methionoine biosynthesis, has been found to use L-vinylglycine (2-amino-3-butenoate) and L-beta-haloaminobutyrates (X = F, Cl) as substrates in addition to the physiological gamma-substituted substrate O-succinyl-L-homoserine (OSHS). Vinylglycine is a substrate both for alpha-ketobutyrate formation (the normal product from gamma elimination with OSHS) and for cystathionine formation (the normal gamma-replacement product with OSHS) in the presence of cysteine. This behavior substantiates that the stabilized vinylglycine--pyridoxal phosphate (PLP) alpha carbanion is the key partitioning species in this enzyme's catalysis. The Vmax values for ketobutyrate production and cystathonine formation from vinylglycine are equivalent at approximately 45 U/mg, whereas the corresponding Vmax values from OSHS are 20 and 200 U/mg, respectively, suggesting different rate-determining steps with these two substrates. The beta-haloaminobutyrates undergo catalyzed HX elimination to yield bound aminocrotonate--PLP directly as a an initial intermediate and as a precursor of ketobutyrate. Little or no cystathionine formation is detectable when these substrates are incubated with enzyme and the normal cosubstrate cysteine, strongly indicating that the aminocrotonate--PLP intermediate is not in rapid, reversible equilibrium with the stabilized vinylglycine--PLP carbanion; in normal catalysis, the prototropic shift from alpha carbanion to aminocrotonate appears functionally unidirectional. The HX-elimination step from beta-chloroaminobutyrate is nonconcerted as demonstrated by a 3H2O in equilibrium chloroaminobutyrate exchange reaction. Further suggestion for discrete beta-halo-alpha-carbanionic intermediates derives from the observation that the haloaminobutyrates appear to a partition between ketobutyrate formation and enzyme inactivation. Since neither vinylglycine nor OSHS causes any detectable inactivation during turnover, it is likely that the inactivation species is not a common intermediate, i.e., the electrophilic aminocrotonate--PLP species (a potential Michael acceptor), but rather a species peculiar to the beta-haloaminobutyrate pathway. The beta-halo-alpha-carbanion--PLP intermediate has beta-halo-alpha-iminodihydropyridine character in the p-quinoid resonance contributor and is a good candidate for an alkylating agent by an SN2--displacement mechanism. Spectroscopic analyses of incubations with the various amino acid substrates show a number of long-wavelength absorbing species forming during turnover, tentative assignments are suggested.

Clinical and laboratory diagnosis of hemostatic disorders in newborn infants

We describe a microtechnology for the study of the coagulation system in newborn infants. Interpretation of results demands an understanding of the techniques used and the nature of the control population from which normal values are drawn. We have examined two syndromes which represent the majority of hemostatic disorders of sick newborn infants. The first is thrombocytopenia resulting from bacterial infections in which there are minimal changes in the levels of blood coagulation factors and little tendency to bleed. The second is a syndrome of disseminated intravascular coagulation in which there is a profound disturbance in the coagulation mechanism, relatively little change in platelet counts, a severe hemorrhagic diathesis, and widespread ischemic necrosis.

The work of a clinical psychologist in primary care

The data presented suggest that general practitioners would be likely to refer a large number of patients with diverse problems to clinical psychologists working in health centres. Compared with a centrally organized clinical psychology service, the work of the primary care psychologist is likely to offer the following advantages:1. Access to psychological help for patients with a need for such help, but who could not attend a central clinic owing to problems associated with travel, work, physical disability, or even a presenting problem such as agoraphobia.2. Greater continuity of care of patients.3. Increased communication between the psychologist and members of the primary care teams.4. Possibility of the psychologist seeing the patient earlier, before the problems have become entrenched.5. Less need for referral to other agencies.6. Reduced stigma for the patient.7. Development of new therapeutic approaches relevant to problems presenting in primary care.8. More flexible and more relevant therapy due to seeing the patients in their home setting.9. Greater therapeutic involvement of the patient's family.10. Reduced costs and inconvenience for the patient's family.11. Reduced administrative and ambulance service costs.While these points do not overcome the need for a formal evaluation of the work of psychologists in primary care, they do suggest that there are advantages in this type of service over the services which are currently available and that a full evaluation would be worth undertaking.