The kinetics of timolol in the rabbit lens: implications for ocular drug delivery

This study examines the uptake and distribution of timolol in the rabbit lens following topical instillation using a heuristic approach. The implications of anisotropic drug diffusion through the lens are presented here and discussed in the context of actual in vivo data. The dynamics of timolol in the lens involve an initial, rapid uptake of the drug by the capsule and epithelium followed by slower, anisotropic diffusion through the cortex body. Kinetically, the capsule and epithelium can be treated as a separate compartment which is distinct from the cortex and which serves to provide a concentration gradient for subsequent diffusion of timolol into the dense interior structures of the lens. Model simulations support the hypothesis that the preferred route of penetration of timolol into the vitreous humor via the lens is the diffusion of drug around the capsule/epithelium and peripheral cortical layers. It is also shown that due to the high and increasing diffusional resistance toward the center of the lens, as well as the diminishing drug concentrations in the capsule and epithelium, steady-state levels in the lens may be extremely difficult to achieve in some therapeutic situations. This phenomenon could have a significant impact on the success or failure of a drug treatment involving the lens and ocular tissues.

A 48 kilodalton intermediate filament associated protein (IFAP) in reactive-like astrocytes induced by dibutyryl cyclic AMP in culture and in reactive astrocytes in situ

In this paper we demonstrate that the 48 kilodalton (kDa) intermediate filament associated protein (IFAP), previously reported to be present in normal astrocytes, is also present in reactive astrocytes in situ and in reactive-like astrocytes induced by dibutyryl cyclic AMP in vitro. This IFAP is detectable by antibodies in normal rabbit serum (F2N) and is closely associated with glial fibrillary acidic protein-containing intermediate filaments (IF). The expression of 48 kDa IFAP is related to the acquisition of stellate shape by normal and reactive-like astrocytes in vitro. It is proposed that 48 kDa IFAP may be responsible for cross-linking IF into bundles and is thereby associated with cell process formation.

Traumatic diaphragmatic hernia: review of 15 cases

From January 1985 to December 1987, 292 laparotomies were performed for injury in Riyadh Central Hospital. Of these, 15 cases were associated with diaphragmatic injuries (5.1 per cent). The diagnosis was missed in 5 cases (30 per cent) and was incidental (at laparotomy) in 3 cases (20 per cent). Therefore in about 50 per cent of the cases, the diagnosis was not made at the initial presentation. In this paper we stress the importance of maintaining a high degree of clinical suspicion in order not to miss traumatic diaphragmatic hernia in multiply injured patients.

Dementia, mental retardation, and competency to make decisions

The psychiatric literature on competency indicates that a diagnosable psychiatric condition alone does not imply incompetency to make treatment decisions. Nonetheless, it is frequently assumed that individuals who are either mentally retarded or demented are incompetent to make decisions. The authors, focusing on the clinical assessment of judgment and decision making, describe two cases. In both, the patients' judgments were intact. The authors conclude: (1) Diagnosis is not the critical factor in determining competency. (2) The process of judgment and decision making has to be assessed on a case by case basis. (3) Further research is needed to develop clinical instruments to assess judgment.

Predictive value of the electroencephalogram in acute hemispheric lesions

We studied the electroencephalogram and computed tomography in twenty cases with ischemic strokes with unilateral electroencephalographic slowing associated with abnormality of background activity on the contralateral side, compared with twenty other cases who had primarily unilateral electroencephalographic abnormality and no contralateral slowing. Electrographic parameters evaluated included field, amplitude, frequency, persistence and reactivity of focal or lateralized slowing. Computed tomographic findings studied included lesion size, density, mass effect and location. Clinical findings studied included level of consciousness and outcome. Contralateral abnormality of background rhythm correlated with impairment of consciousness and poor outcome.

Mitral annular calcification and coarctation of aorta

Although coarctation of the aorta is associated with various cardiac abnormalities, its association with mitral annular calcification (MAC) is not reported. We therefore report a 37-year-old patient with postductal coarctation of the aorta and MAC. Considered to be a degenerative process, MAC is usually seen in elderly patients. It is uncommon in patients less than 50 years old and rare before the age of 40 years. Previous studies have reported increased frequency of cardiac conduction disturbances in patients with MAC compared to age- and sex-matched controls. This is in agreement with complete right bundle-branch block noted on the electrocardiogram of our patient. Clinicopathologic correlative studies and long-term follow-up may determine how such conduction disturbances develop and progress.

Association of double NOR variant with Turner syndrome

A study was made of the possible association of double nucleolus organizers (dNORs) with Turner syndrome. Occurrence of dNORs was determined using the silver staining method of Goodpasture and Bloom [1975]. In 45 control subjects, the incidence of dNORs was 8.8%. Studies were done on 33 Turner syndrome patients. In 28 cases with 45,X or 45,X/46,XX karyotypes, the incidence of the dNOR variant was 50%. Five cases of Turner syndrome with X rings or X isochromosomes were negative for dNORs. Analysis of the data indicates an association between the dNOR variant and the occurrence of Turner syndrome. It is proposed that the presence of the dNOR variant can increase the rate of nondisjunction of the X chromosome in meiosis or in mitotic divisions during early gestation.

Use of somatosensory evoked responses in the prediction of outcome from coma

Present data on 60 comatose patients with head trauma, hypoxia and cerebrovascular disease suggested that SER may yield quantitative, useful information concerning the functional state of the cerebral cortex. To assess the prognosis of individual patients we propose to classify patients from various etiologies of coma into the following categories: I. If there is bilateral absence of cortical responses, irrespective of the etiology of coma, none of these patients recover. II. If the initial cortical responses in the first 24 hours are normal, then it is imperative that these should be repeated in the first week before any definitive prognosis can be given, (since as in one case, we noted on the fifth day there was distortion of amplitude of his response and eventually the cortical responses were unobtainable, therefore indicating a poor prognosis). III. Patients who have normal responses throughout the acute course of illness carry an excellent prognosis from coma of all etiologies, except with ischemic etiology. The prognosis remains favorable for recovery from coma, but these patients may remain with significant neurological deficits. IV. When there is a 75% drop in the amplitude of the responses, it indicates a poor prognosis for ultimate neurological recovery, and the majority of these patients will remain in a persistent vegetative state. V. In patients with intermediate reduction in amplitude, 25-50% carried a moderate prognosis, and the majority of these cases in our series were able to perform activities of daily living.

Absence status epilepticus resulting from metrizamide and omnipaque myelography

Two cases of absence status are described, one case following metrizamide myelography and the other from omnipaque myelography. Metrizamide has been well known to cause convulsive seizures even in patients without epilepsy. The exact mechanism is not known but appears to be direct neuronal toxic effects possibly due to competitive inhibition of hexokinase activity. The acute confusional state following myelography from water soluble agents is reviewed. In view of the difficulty in clinical diagnosis and the excellent response to anticonvulsant therapy, the possibility of this clinical entity should be specifically excluded by EEG in any person suffering from prolonged confusion following myelography with water soluble agents.

Reversible depression in Binswanger's disease

The authors describe four elderly patients with Binswanger's disease in whom depression was prominent. Therapy with antidepressant drugs in three patients produced major improvement in psychological and physical functions. The one patient who could not be given an adequate course of antidepressant therapy because of intercurrent illness improved spontaneously after many months. The authors conclude that depression associated with Binswanger's disease is reversible despite persistence of neurological abnormalities. They speculate that this depressive syndrome is an example of organic affective disorder due to diffuse subcortical white matter ischemic lesions of the cerebral hemispheres and discuss the possible neuroanatomical basis of the depression.

48-Kilodalton intermediate-filament-associated protein in astrocytes

We provide evidence that a protein of 48 kilodaltons (KD), recognized by a normal rabbit serum (F2N), is associated with intermediate filaments (IF) of astrocytes both in cell cultures and in situ. Immunofluorescence staining shows that the F2N serum gives a fibrous staining pattern similar to that seen with anti-serum to glial filament protein (GFP), a protein specific for IF of astrocytes, and that both proteins are present in the perinuclear fibrous aggregates of IF produced by treating the cells with colchicine. At the ultrastructural level the gold particles decorating the 48-KD protein are localized in clusters along the IF, whereas the gold particles decorating the GFP are localized on the IF in a linear pattern. This difference in distribution and the fact that the two proteins have different electrophoretic mobilities on SDS gels indicates that the 48-KD protein although associated with IF is different from GFP. The 48-KD protein appears to be a distinct, developmentally regulated intermediate-filament-associated protein (IFAP), different from other IFAPs reported to date and the first IFAP described in astrocytes. Its appearance in late developmental stages when motile astroblasts are changing into nonmotile stellate cells suggests that the 48-KD protein may be involved in cross-linking the GFP-containing IF to provide more tensile strength to the cytoplasm at the expense of flexibility.

Bacteriological quality of raw human milk: effect of storage in a refrigerator

Eighty-seven breast milk samples were obtained from 63 mothers of infants on the neonatal intensive care unit of the Lagos University Teaching Hospital. The samples were cultured for bacteria immediately after collection (0 h) and then stored in a domestic refrigerator from where cultures were repeated at 6-hourly intervals for 24 h. At 0 h, three (3.4%) of the samples were sterile; 56 (64%) grew coagulase negative staphylococci, and one (1.1%) Streptococcus viridans. Thus, 60 (69%) of the samples were either sterile or contained only skin commensals. Twenty-nine (31%) grew potential pathogens--coagulase positive staphylococci in two (2.3%) and mixed growth of staphylococci, coliforms and klebsiella in 25 (28.3%). During the 24 h storage in the refrigerator, bacteria multiplied in 50 and their growth was inhibited in 32 of the samples. But the mean bacterial count at any time during the 24 h was not significantly different from that at the beginning of the storage in the refrigerator. It is proposed that expressed breast milk stored in a domestic refrigerator can be given safely to infants within 24 h of collection if heavy contamination is prevented at the time of collection.

Stability of cefazolin sodium in various artificial tear solutions and aqueous vehicles

The stability of cefazolin sodium reconstituted in four artificial tear solutions, two acetate buffer solutions, phosphate buffer solution, and 0.9% sodium chloride injection was studied. Cefazolin was reconstituted in Tearisol, Isopto Tears, Liquifilm Forte, and Liquifilm Tears; acetate buffer solution at pH 4.5 and pH 5.7; phosphate buffer solution at pH 7.5; and 0.9% sodium chloride injection. The solutions were stored at 4 degrees C, 25 degrees C, and 35 degrees C for seven days. All of the solutions were inspected for particulates, turbidity, color, and odor. Five assay determinations on each of three samples of each formulation were performed using a stability-indicating high-performance liquid chromatographic assay. Cefazolin stability was influenced primarily by pH and storage temperature. Reconstitution of cefazolin sodium in the alkaline tear solutions Isopto Tears and Tearisol and in phosphate buffer solution resulted in particulate and color formation at 25 degrees C and 35 degrees C. Turbidity was noted after cefazolin sodium was reconstituted in Isopto Tears. No color or precipitate formation was evident after seven days at 25 degrees C and 35 degrees C in the formulations of acidic pH containing Liquifilm Tears, Liquifilm Forte, 0.9% sodium chloride injection or acetate buffer solution as the vehicles. The extent of degradation of cefazolin was substantially higher in the formulations of alkaline pH than in those of acidic pH at 35 degrees C and 25 degrees C. All of the formulations retained more than 90% of their initial concentration when stored at 4 degrees C. Cefazolin sodium, when reconstituted in artificial tear solutions with an acidic pH, is stable for up to three days at room temperature.

Calcific valvular aortic stenosis with and without mitral anular calcium

Seventy-six consecutive patients, mean age 66 +/- 9 years (+/- standard deviation), with isolated aortic valve replacement for calcific valvular aortic stenosis (AS) were studied. Mitral anular calcium (MAC) was detected by echocardiography in 45 patients (59%). Patients with MAC were older (p less than 0.01), had greater peak systolic aortic valve gradients (p less than 0.025), lower cardiac indexes (p less than 0.025) and smaller valve areas (p less than 0.05) than patients without MAC. Thirty-three percent of patients (15 of 45) with MAC required permanent pacemaker implantation after aortic valve replacement, compared with only 10% of patients (3 of 31) without MAC (p less than 0.025). During the follow-up of 7 years (mean 3.8 +/- 1.6), 27% of patients (12 of 45) with MAC died from cardiac causes, compared to only 7% (2 of 31) without MAC (p less than 0.025). Thus, patients with AS and MAC are older, have more severe AS, more frequently undergo permanent pacemaker implantation after aortic valve replacement and more frequently die of cardiac causes than patients with AS and no MAC during follow-up.

Physicochemical determinants of drug diffusion across the conjunctiva, sclera, and cornea

This investigation examined some of the barrier properties of the conjunctival, scleral, and corneal membranes. The diffusion of nadolol, timolol, propranolol, penbutolol, sucrose, and inulin was measured across the isolated corneal and scleral membranes of the rabbit using a two-chamber glass diffusion cell. Drug absorption across the cornea and the conjunctiva was studied in vivo by measuring precorneal drug clearance. The drug samples were analyzed either by HPLC or liquid scintillation counting (LSC). For all the compounds tested, the scleral permeability was significantly higher than the respective corneal permeability. The permeability coefficients of the beta-blockers varied in the following manner: propranolol > penbutolol > timolol > nadolol for the cornea, and penbutolol > propranolol > timolol > nadolol for the sclera. The cornea offered substantially more resistance to inulin, a polar, macromolecular substance, than did the conjunctiva. However, the cornea and conjunctiva offered comparable resistance to the smaller and less polar drug timolol. This information may serve as a basis for optimizing the intraocular delivery of drugs that are poorly absorbed across the cornea due to their physicochemical properties.

Organization of microfilaments in astrocytes that form in the presence of dibutyryl cyclic AMP in cultures, and which are similar to reactive astrocytes in vivo

This paper deals with changes in the arrangement of microfilaments at various stages during the transformation of astroblasts into reactive astrocytes in the presence of dibutyryl 3',5'-cyclic adenosine monophosphate in vitro. When cultures of two-week-old mouse astroblasts are treated with dibutyryl cyclic AMP, drastic changes occur in cell shape and in the organization of microfilaments, resulting in cells that closely resemble reactive astrocytes in vivo. A thick, prominent ring of microfilaments in such cells which stains strongly with 7-nitrobenz-2 oxa-1,3-diazole-phallacidin, delineates the perikaryon. Electron microscope examination showed that the ring is composed of many smaller bundles of microfilaments running parallel to each other. Prominent bundles of microfilaments radiate from the cell body into the cell processes. Based on the observation of intermediate forms, we propose that the microfilament ring may be important in the development of cell processes in reactive astrocytes.

Mechanism of action of some bioreducible 2-nitroimidazoles: comparison of in vitro cytotoxicity and ability to induce DNA strand breakage

The interaction of a series of nitroimidazole-aziridine radiosensitisers, as parent or radiation-reduced species, with plasmid DNA in aqueous solution at pH7 results in strand breakage. The efficiency of strand breakage substantially increases on reduction of the nitroimidazole analogues. The rate of production of strand breaks decreases on interaction with both parent and reduced nitroimidazole analogues as the aziridine moiety is deactivated through alkyl-substitution. These variations in efficiency are reflected in changes in the toxicity towards both oxic and hypoxic cells and in the decrease in toxicity with progressive substitution of the aziridine moiety. The stabilities of these nitroimidazoles in aqueous solution at pH7 have also been determined. However, these stabilities do not parallel the variations in the alkylating efficiency of DNA by the aziridine moiety. These results have been discussed in terms of the relative reactivities of the nitroimidazoles with plasmid DNA and their ability to act as cytotoxic agents, especially following bioreduction and how the findings may relate to the radiosensitising properties of these agents.

A geriatric neuropsychiatric inpatient unit

Geriatric neuropsychiatry units have been developed in hospitals in various parts of the United States to provide an intensive diagnostic and treatment program for geriatric patients who have behavioral problems or the early signs of dementia. The Geriatric Neuropsychiatry Unit at the Boston City Hospital is described as a model unit. The process of patient selection and admissions criteria are outlined. Diagnostic interventions and the full evaluative process are then presented, followed by a summary of the therapeutic interventions. These interventions include pharmacologic, psychotherapeutic, behavioral, and milieu therapies. The communications process essential for effective multidisciplinary team function is also reviewed. Discharge planning procedures are presented, along with a summary of patient outcomes.

Induction of DNA strand breaks by reduced nitroimidazoles. Implications for DNA base damage

Radiation-reduced 2-nitroimidazoles (misonidazole, RSU-1137, Ro.03-8799 and Ro.03-8800) incubated in air with plasmid DNA (pH 7.0, 310K) induce DNA strand breakage, as revealed following subsequent heat or alkali treatment. Only RSU-1137 resulted in the binding of a [2-14C] fragment and significant yields of heat-labile strand breaks (greater than 20% loss of type-I DNA after 48 hr incubation). RSU-1137 was shown to be greater than 6 times more effective than misonidazole at producing alkali-labile breaks. In fact, the efficiency of alkali-induced strand break production is in the order: misonidazole less than Ro.03-8799 approximately Ro.03-8800 less than RSU-1137. Reaction of these reduced 2-nitroimidazoles with 2'-deoxyguanosine (dG) also results in the formation of a common glyoxal-dG product, with its yield and rate of production being dependent upon the 2-nitroimidazole used. It has been demonstrated that these variations are influenced by the N-1 side-chain of the 2-nitroimidazole. Product yields are approximately 5-6 times greater with misonidazole than with RSU-1137. From the evidence presented, it is apparent that formation of glyoxal (or a glyoxal-like product) is not responsible for the DNA strand breakage seen. It is inferred that these breaks are induced by a nitro-reduction product(s) which remains unidentified.

Analogues of RSU-1069: radiosensitization and toxicity in vitro and in vivo

A series of nitroimidazoles containing aziridine and alkyl-substituted aziridine functions has been synthesized. The 2-nitroimidazole compounds examined all show greater radiosensitizing efficiency in vitro than misonidazole. The 4- and 5-nitroimidazole analogues are also more efficient than equivalent compounds which do not contain the alkylating aziridine moiety. All the compounds show increased toxicity towards hypoxic cells relative to aerobic cells, but this toxicity is reduced by alkyl-substitution of the aziridine ring. In vivo toxicity can also be reduced by modification of the aziridine function, but such alterations appear to have less effect upon the high radiosensitizing efficiency of these compounds in vivo. As a consequence of this study, compounds of potentially improved therapeutic utility compared to RSU-1069, the first reported member of this class, have been identified.

Routine or selective peroperative cholangiography

The routine use of peroperative (pre-exploration) cholangiography was prospectively studied in 433 consecutive patients undergoing elective cholecystectomy. Satisfactory peroperative cholangiography was achieved in 396 patients using a C-arm image intensifier with image retention facility. Clinical indications for exploration of the common bile duct were noted for each patient but the decision for choledochotomy was determined by the cholangiographic results. Two hundred and forty-nine (63 per cent) patients had no clinical indications for duct exploration and cholangiographic findings were all normal. Of the 147 patients with positive clinical criteria, 39 (9.8%) had abnormal cholangiograms and required exploration of the common bile duct. In three patients duct exploration was negative giving a false positive rate of 0.73 per cent. The use of the image intensifier allowed dynamic study during cholangiography and optimum evaluation of the duct system. The results support the view that peroperative cholangiography could be restricted to patients with clinical indications for exploration of the common bile duct.

Studies on the mechanisms of the radiosensitizing and cytotoxic properties of RSU-1069 and its analogues

RSU 1069 is a substantially more efficient sensitizer than misonidazole when hypoxic Chinese hamster V79 cells are irradiated in vitro at room temperature; such that for 0.5 mmol dm-3 sensitizer an ER of 3.0 is obtained for RSU 1069 whereas an ER of only 1.6 is obtained for misonidazole. However, when irradiation is done at 4 degrees C, the radiosensitization caused by RSU 1069 is reduced to a level close to that obtained with misonidazole, the action remaining unaltered at the lower temperature. This temperature dependent component of sensitization for RSU 1069 suggests the involvement of a slow biochemical process that has an appreciable activation energy. The RSU 1069 analogue RB 7040 is a more efficient radiosensitizer than RSU 1069 particularly at lower concentrations. This compound has a pKa value of 8.45, in contrast to that of RSU 1069 which is 6.04. Weak bases with pKa values in excess of average intra-cellular pH can be taken up preferentially into cells from medium at pH 7.4. It is shown that RB 7040 has a 4 X higher intracellular concentration than RSU 1069 for a similar extracellular concentration. This will explain, at least in part, the greater sensitizing efficiency of this compound when compared to RSU 1069 in vitro.

Experimental pharmacokinetics of RSU-1069 and its analogues: high tumor/plasma ratios

The mixed-function radiosensitizer RSU-1069 and its analogues possess both alkylating and electron-affinic properties, and have been shown to be more efficient radiosensitizers than misonidazole both in vivo and in vitro. The pharmacokinetics following intraperitoneal injection of three members of this series, RSU-1069, RSU-1164, and RSU-1172 have been studied in C57BL mice bearing B16 melanoma. Peak tumor levels of each compound, and tumor/plasma ratios (T/P) were found to be high: T/P RSU-1069 = 3.8, RSU-1164 = 3.7; RSU-1172 = 4.0. In contrast, other normal tissues including brain showed tissue/plasma ratios close to 1. The mechanisms responsible for differential tumor uptake are unknown, but may depend on the basicity of the compounds, leading to preferential uptake in areas of low pH, or alternatively they may be associated with the alkylating function. This group of compounds appear to demonstrate highly favorable tissue distributions.

The mechanisms of target cell injury by nephrotoxins

Hexachlorobutadiene-N-acetylcysteine (HCBD-NAC), adriamycin and 2-bromoethanamine hydrobromide are three renal toxins that have shown in vivo a highly selective target cell toxicity--to the proximal tubules, the glomerular epithelial cells and the medullary interstitial cells, respectively. To study some aspects of the mechanisms of this selective toxicity, the three types of target cell were isolated from the kidneys of Wistar rats, and cultures of the cells or tissue fragments were exposed to various concentrations of the three toxins. Using fluorescence microscopy combined with enzyme and histochemical probes, the selective target-cell toxicity of the three compounds already established in vivo was demonstrated also in vitro. Moreover, the in vitro toxic effect of HCBD-NAC was ameliorated by probenecid, as is the case in vivo. Several functional characteristics specific to each of the target cells, such as the selective uptake of a toxin, the presence of lipid droplets and the level of peroxidative enzyme activity, have been identified as probable factors in the occurrence of the target cell necrosis.

Substance-induced organic mental disorders. A clinical and conceptual approach

Drug abuse is a prevalent problem in society and often occurs as abuse of multiple substances. The authors present a model for understanding the clinical symptomatology and course of substance-induced organic mental disorders and present a hypothesis that explains how various factors might interact to produce the disorder. A clinical case is used to illustrate the use of this approach and suggestions are made for the diagnosis and treatment of these disorders.

Neonatal necrotizing enterocolitis in Lagos

The records of 14 infants in whom the diagnosis of Neonatal Necrotizing Enterocolitis was made between 1978 and 1984 were studied. The distance appeared in the second week of life of the majority (57%) of the babies, and was equally prevalent in preterm and term babies. Infections seemed to be the predisposing factor in all cases although no transmissable pathogens were identified. Abdominal distention (57%), rectal bleeding (21%) and bowel perforation (14%) were the main presenting features. The only three survivors were among the babies treated medically including intravenous metronidazole. The only baby that survived bowel resection succumbed three months later to jejunostomy diarrhoea. Extended medical management including intravenous metronidazole is being suggested as the treatment for acute NNEC in developing countries while surgical treatment is reserved only for perforation and uncontrollable rectal bleeding.

The interaction between radiation and complexes of cis-Pt(II) and Rh(II): studies at the molecular and cellular level

A range of Rh(II) carboxylates and cis-Pt(II) complexes have been examined for their ability to increase the radiation sensitivity of aerobic and hypoxic V79 cells in vitro. The transition metal complexes sensitize in both air and nitrogen, with the greater effect generally occurring in nitrogen. The cis-Pt(II) complexes only show small levels of sensitization with dose modification factors (DMFs) of no more than 1.2. In contrast, the Rh(II) complexes can give DMFs of 2.0. Radiation chemical experiments show the transition metal complexes to have substantially lower redox potentials than metronidazole and, in addition, neither type of complex undergoes electron transfer reaction or adduct formation on interaction with radicals derived from DNA bases. Thus, the inorganic complexes do not operate by mechanisms similar to those occurring with electron affinic or stable free radical sensitizers. The increase in radiation sensitivity for cells treated with the Rh(II) carboxylates, but not the cis-Pt(II) complexes, is attributed to the ability of the Rh compounds to deplete intracellular thiols. Further, the efficiency of sensitization by the Rh(II) complexes and their ability to interact with cellular thiols depends upon the nature of the carboxylate ligand and follows the order butyrate greater than propionate greater than acetate greater than methoxyacetate. The differences between the carboxylates may be due to differences in drug uptake. A combination of the Rh(II) complexes with misonidazole given to hypoxic cells irradiated in vitro gives an additive response. However, it was not possible to demonstrate a similar effect in tumours in mice given the combination of Rh(II) methoxyacetate and the misonidazole analogue RSU 1070.

The development of bacterial flora of premature neonates

The sequential acquisition of bacterial flora by premature neonates was studied during a 10 month period. Mean gestational age of the babies was 29.01 weeks and the mean birth weight was 1.728 kg. Escherichia coli and group B streptococci (GBS) colonized the umbilicus of 7 and 6 babies respectively, out of 23 studied, on the first day of life. E. coli and staphylococci were the predominant flora on the 6th day and they colonized 12 and 13 respectively. The oral flora was predominantly Gram-positive cocci, mainly Streptococcus salivarius which was isolated from 17 out of 22 babies on the 6th day, viridans streptococci were isolated from 14 babies, Staphylococcus albus from 16 babies and group D streptococci from 11 babies. Candida spp. also colonized the oral cavities of 17 out of 22 babies on the 6th day. At the end of the first week of life, the faecal flora was predominantly anaerobic represented by Bifidobacterium spp., Bacteroides spp. and Clostridium spp. The commonest facultative faecal flora were E. coli, which was isolated from all the babies, and Strept. faecalis isolated from 20 babies. Early gut colonization by GBS, Bacteroides spp. and Clostridium spp. was noticed in more babies delivered vaginally than by caesarean section where colonization by these bacteria was relatively delayed. The use of prophylactic penicillin plus gentamicin in the special neonatal unit probably prevented systemic spread of any of the potential opportunistic pathogens during the study.

Importance of the noncorneal absorption route in topical ophthalmic drug delivery

Transcorneal permeation has traditionally been the mechanism by which topically applied ophthalmic drugs are believed to gain access to the internal ocular structures. Relatively little attention has been given to alternate routes by which drugs may enter the eye. A system has been developed which allowed the investigation in vivo of the contribution of noncorneal absorption to intraocular drug levels after topical dosing. Using timolol and inulin as probe drugs, it was shown that the noncorneal absorption route may contribute significantly to drug penetration into intraocular tissues. Furthermore, results demonstrated that drugs absorbed by the noncorneal route appeared to enter certain intraocular tissues by a mechanism which bypasses the anterior chamber. These studies suggested that intraocular penetration via noncorneal routes involves penetration of drug across the conjunctiva/sclera. Neither reentry from the general circulation after drug absorption into the blood or drug delivery by the local vasculature accounted for the observed results. In terms of topical ophthalmic drug delivery, the noncorneal absorption route may be important for drugs that are poorly absorbed across the cornea due to their physical-chemical properties. We have demonstrated this using inulin as a model for a poorly absorbed, high molecular weight substance.

RSU 1069, a 2-nitroimidazole containing an alkylating group: high efficiency as a radio- and chemosensitizer in vitro and in vivo

Electron affinity as measured by the one-electron reduction potentian, E7(1), is the major factor influencing radiosensitizing efficiency in vitro. RSU 1069 has an electron affinity (E7(1) = 398 mV) similar to misonidazole; however, the ability of this compound to sensitize hypoxic cells is considerably greater in vitro than that of misonidazole, e.g., 0.2 mM RSU 1069 gives an enhancement ratio of greater than 2.0 compared to 1.4 for the same concentration of misonidazole. Radiosensitization studies with the MT tumor in vivo also showed RSU 1069 to be a more efficient sensitizer than misonidazole. An administered dose of 0.08 mg/g RSU 1069 yielded an enhancement of 1.8 to 1.9 using tumor cell survival and tumor cure as end-points. At least a 10-fold higher dose of misonidazole is required for a similar degree of sensitization. Low doses of RSU 1069 also radiosensitize the Lewis lung and B16 experimental tumors. The ability of RSU 1069 to potentiate the cytotoxic action of melphalan and other cytotoxic drugs towards the MT tumor was also examined. RSU 1069 (0.08 mg/g) given to mice 1 hour before melphalan gave an enhancement of 2.8.

Tradescantia-Micronucleus (Trad-MCN) tests on 140 health-related agents

The Tradescantia-Micronucleus (Trad-MCN) test is a simple short-term bioassay for various gaseous and liquid forms of chemical agents, and physical agents such as radiation. 140 agents, directly or indirectly related to human health, were screened for their mutagenicity. Plant cuttings of young inflorescences, in which the pollen mother cells undergo various stages of meiosis, were maintained in nutrient solution for experimentation. Treatments were made either by absorption of the soluble agents through the stem, by diffusion of gaseous agents through the leaves and buds, by exposure to internal/external radiation or by in situ exposure to air pollutants. Micronuclei formed from damaged chromosomes served as the indicators of mutagenicity. Results of 140 agents tested are listed in 9 different categories. (1) Carcinogens/mutagens, (2) common beverages, (3) common chemicals, (4) drugs, (5) pesticides, (6) common household chemicals, (7) radiation and radioisotopes, (8) in situ monitoring, (9) complex environmental mixtures. Out of 140 agents tested, 52 showed positive, 20 showed borderline positive responses and 5 showed strong toxicity. Test results of 41 agents in the present study showed 67% congruity with Ames test results found in the literature.

Potentiation of cyclophosphamide cytotoxicity in vivo: a study with misonidazole and fifteen other 1-substituted 2-nitroimidazoles

It has recently been reported that compounds more lipophilic than misonidazole are better potentiators of CCNU tumor cytotoxicity in vivo. There is now a need to extend these studies to include other tumors and cytotoxic drugs. In the present study we have shown that misonidazole (MISO) can potentiate cyclophosphamide cytotoxicity in the Lewis lung carcinoma but not in the B16 melanoma. Further studies in the Lewis lung carcinoma, using 15 1-substituted 2-nitroimidazoles possessing a range of octanol:water partition coefficient (P) (from 0.18- greater than 100) have shown that potentiation increases with increasing lipophilicity. The most efficient compounds at administered dose levels of 1.0 and 2.0 mumol/g were Ro-07-1902, benznidazole (Ro-07-1051) and RSU 1050 which possess octanol:water partition coefficients in the range of 2.5-10. However, on the basis of an equitoxic administered dose (1/2LD50/2d), little difference in potentiation is seen over the range of P studied.

Radiosensitization of mammalian cells by transition metal complexes containing nitroimidazole ligands

Various transition metal complexes containing nitroimidazoles as ligands have been shown to act as radiosensitizers of hypoxic cells in vitro. Sensitization by cis-Pt(II)Cl2 (nitroimidazole)2 complexes is no greater than that which can be demonstrated by the free nitroimidazole ligand alone. These results differ from those previously described for the compound FLAP where an ER of 2.4 was obtained at a concentration of 50 microM. We report that, even using the same treatment technique, the maximum ER that can be achieved is 1.2. Further, the sensitizing efficiency of FLAP cannot be improved when cells are kept in contact with the compound for 12 hours in air prior to deoxygenation and irradiation. In contrast, Rh(II) complexes show much greater sensitization than can be obtained with the free ligand and these compounds are in turn more efficient sensitizers than the comparable Pt(II) complexes.

Radiation sensitization and chemopotentiation: RSU 1069, a compound more efficient than misonidazole in vitro and in vivo

Electron affinity as measured by the one-electron reduction potential, E17, is the major factor influencing radiosensitizing efficiency in vitro. RSU 1069 has an electron affinity (E17 = -398 mV) similar to misonidazole; however, the ability of this compound to sensitize hypoxic cells is considerably greater than that of misonidazole, e.g. 0.2 mM RSU 1069 gives an enhancement ratio of 2.2 compared to 1.5 for the same concentration of misonidazole. Radiosensitization studies with the MT tumour in vivo also showed RSU 1069 to be a more efficient sensitizer than misonidazole. An administered dose of only 0.08 mg g-1 RSU 1069 yielded an enhancement of 1.8 to 1.9 using tumour cell survival and tumour cure as end-points. The ability of RSU 1069 to potentiate the cytotoxic action of melphalan towards the MT tumour was also examined. RSU 1069 (0.08 mg g-1) given to mice 1 h before melphalan resulted in an enhancement of 3.0. In contrast, previous studies had shown with a series of nitroimidazoles including misonidazole that Ro 03-8799 was the most effective potentiating agent, but this only gave an enhancement of 2.3 at a 10-fold higher dose than RSU 1069. RSU 1069 is a compound of substantial promise both as a radiosensitizer and chemopotentiating agent and warrants further investigation.

Brainstem auditory evoked potentials in dizziness

To investigate the role of brainstem dysfunction in patients with dizziness, Brainstem Evoked Responses were recorded, and results of 100 such cases are presented. The present study further emphasizes the fact that dizziness is a symptom complex and careful evaluation of these patients is necessary. If a systematic approach is used, then a correct diagnosis can be achieved in over 95% of the cases. Vascular insufficiency of the brainstem can present as dizziness and may precede a catastrophic vascular infarction by weeks and months. Early recognition of the problem is of paramount importance, since anticoagulation therapy can be started early or other surgical correctable measures can be undertaken to prevent catastrophic infarction.

Radiosensitization in vivo: a study with an homologous series of 2-nitroimidazoles

An homologous series of 1-(omega-morpholino)alkyl-2-nitroimidazoles, previously reported to be more efficient hypoxic cell radiosensitizers than misonidazole (MIS) in vitro, were evaluated in vivo using the murine Lewis Lung carcinoma. When given i.p. the compounds were 3-20 times more acutely toxic (LD50/2d) than MIS and this toxicity increased with both the number of methylene groups (n) in the side chain and the lipophilicity of the compounds. The compounds sensitized the tumour to single doses of X-rays. On the basis of equimolar administered dose, the most effective compounds, n = 2, 4 and 5, were as efficient as MIS. However, on the basis of the measured concentration of drug in the tumour at the optimum time of irradiation the compounds with n = 4 and n = 5 were less efficient than expected from previously published data in vitro. This is attributed to the basicity of the morpholino nitrogen in these compounds such that at physiological pH the compounds are primarily in an ionized form and hence poorly able to penetrate hypoxic cells.

Studies on the photostability of reserpine in parenteral solutions

The photostability of reserpine in several parenteral formulations has been studied and the effects of some commonly used stabilizers have been evaluated. The kinetic data indicate that the photodegradation of reserpine follows zero order kinetics in all the formulations at pH = 2 and 3. The stability of reserpine appears to be higher at pH = 3 than at pH = 2. 3-dehydroreserpine, isoreserpine and lumireserpine were identified as the major photodegradation products by TLC, suggesting that the photodegradation in acidic solutions occurs initially via an oxidative mechanism. The combined effect of EDTA and PABA on the photostability of reserpine was more significant than their individual effect. The formulations in which benzyl alcohol was used as vehicle were found to be more stable than those having propylene glycol. Polyethylene glycol was found to be a better surfactant than Tween 80. The degree of stabilization in the presence of surface active agents has been explained in terms of micellar theory and the degree of hydration of micelles. A stable formula for parenteral solution of reserpine has been suggested.