Timecourse of oocyte development in saithe Pollachius virens.

Wild caught North Sea saithe Pollachius virens were monitored for growth, sex steroid profiles and oocyte development pre-spawning and measured for egg size and group fecundity during the spawning season in the laboratory. Vitellogenesis commenced in late October-early November, at a leading cohort size (CL ) of c. 250 µm, after which oocytes grew rapidly in size until spawning started in February. Notably, a distinct cortical alveoli stage was virtually absent with yolk granules observed in developing oocytes at the very beginning of vitellogenesis. Little atresia was observed pre-spawning, but atretic re-absorption of remnant oocytes containing yolk granules was found in all females immediately post-spawning. As expected, concentrations of sex steroids, oestradiol-17ß (females), testosterone (both sexes) and 11-ketotestosterone (both sexes), increased pre-spawning before dropping post-spawning. The present experiment provides the first validation of sex steroid levels in P. virens. Post-ovulatory follicles were visible in histological sections from female gonads 9-11 months post-spawning, but then disappeared. Spawning commenced around a CL of c. 750 µm (700-800 µm). Hydrated oocytes (eggs) measured between 1·04 and 1·31 mm (mean = 1·18 mm) with decreasing sizes towards the end of spawning. The average estimated realized fecundity was c. 0·84 million eggs (median female total length, LT = 60 cm). Spawning lasted from 13 February to 29 March.

Losing the housing game. The leveling effects of substance abuse.

Analysis of the housing dynamics and individual characteristics of a sample of 670 participants in the New Orleans Homeless Substance Abusers Program reveals substantial diversity with respect to income, education, and occupational attainment. Nevertheless, drug consumption and dependence serve as socioeconomic levelers, dissolving otherwise potentially critical differences in human-capital and economic capacities. The need to focus concurrently on both structural and individual causes of homelessness is emphasized.

Reliability and validity of the addiction severity index among homeless substance misusers.

Retrospective self-reports of behavior are widely used in alcohol and drug research. However, assessments of the reliability and validity of such data among certain populations are nonexistent. This study examines the ability of the Addiction Severity Index (ASI), a widely used clinical and research instrument, to provide valid and reliable data within a homeless population of drug misusers. The results support the usefulness of the ASI in producing quality data among homeless substance misusers seeking treatment. Qualitative data gathered from field interviewers are used to highlight strategies for enhancing the quality of ASI data in the future.

Morphological alterations in the hippocampus following hypobaric hypoxia.

1. The morphological consequences of hypobaric hypoxia, exposure to reduced pressure atmospheres, were examined in the hippocampus of male Fischer 344 rats. Severe chronic hypoxia can produce permanent neuronal damage with hippocampal structures being especially vulnerable. 2. Hippocampal morphology was studied using histological observations after a 4 day exposure to sea level, 3500 m, or 6400 m. Two groups tested at 6400 m were sacrificed at different intervals following exposure, 72 and 144 h, to examine the effect of post-exposure time on neuronal damage. 3. Histological damage was observed in rats' brains following exposure to altitude, with cell degeneration and death increasing as altitude increased. In addition, it was found that the longer the time following exposure before sacrifice, the more noticeable the damage, suggesting delayed neurotoxicity. Increases in the number of damaged cells following altitude were significant for the CA3 region of one 6400 m group; however, other differences did not reach statistical significance. Rats exposed to altitude for 4 days ate less and lost significantly more weight than did animals at sea level. 4. It appears that 4 days of exposure to altitudes less than or equal to 6400 m does produce changes in the CA3 subfield, but the damage is different than that seen with other models of non-transient ischemia.

Housing dynamics of the homeless: implications for a count.

Housing dynamics of homeless people limit all efforts to count them. Data on 60-day housing histories from a sample of homeless substance abusers in New Orleans show that homeless people spend relatively few nights in locations that would make them potentially countable, no matter how thorough the enumeration procedure.

Factors that interact with treatment to predict outcomes in substance abuse programs for the homeless.

This paper reviews the main treatment effects observed in the New Orleans Homeless Substance Abusers Project and then analyzes and discusses factors that appear to interact with treatment to produce successful treatment outcomes. Outcomes are assessed for alcohol and drug use, housing stability, and employment. Results show marginally significant positive effects for long-term treatment, but only for clients retained in treatment for more than about three months. Holding treatment variables constant, client characteristics that predict successful treatment outcomes include gender, education, age, psychiatric morbidity, drug of choice, attendance at AA/NA meetings, and prior treatment histories. Some of these same factors also predict success among controls. The significance, sign, and magnitude of these effects, however, varies depending on which specific outcome one analyzes. Thus, variation in treatment effectiveness is associated with entering conditions, as the literature suggests, but which entering conditions matter most depends on which specific outcome one examines.

Hypobaric hypoxia impairs spatial memory in an elevation-dependent fashion.

The effects of various levels of hypobaric hypoxia, exposure to reduced atmospheric pressure, on spatial memory in rats were examined. Hypobaric hypoxia simulates high altitude conditions where substantial deficits in human cognitive performance occur. However, few studies have measured cognitive changes in animals during exposure to this type of hypoxia. Male Fischer 344 rats were tested in the learning set version of the Morris water maze, a test known to assess spatial memory. Rats were tested at 2 and 6 hours while exposed to a range of simulated altitudes: sea level, 5500 m, 5950 m, and 6400 m. Altitude exposures at 5950 or 6400 m decreased both reference and working memory performance, as demonstrated by latency, distance, and speed measures, in an elevation-dependent fashion. During sea level testing on the day following hypobaric exposure, decrements in reference memory were still observed on all dependent measures, but only speed was impaired on the working memory task. These results agree with human studies that demonstrate elevation-dependent impairments in spatial memory performance during exposure to hypobaric hypoxia. The deficits may be attributable to changes in hippocampal cholinergic function.

Nimodipine prevents the in vivo decrease in hippocampal extracellular acetylcholine produced by hypobaric hypoxia.

Hypoxia decreases acetylcholine (ACh) synthesis and release in vitro, and ACh synthesis in vivo; however, its effect on extracellular concentration of ACh in vivo is not known. The calcium channel blocker nimodipine is a cerebrovascular dilator which also increases extracellular ACh in vivo. Therefore, it may provide protection from the effects of hypobaric hypoxia on the cholinergic system either via its effects on vascular function or by direct action on the nervous system. This study examined the effect of hypobaric hypoxia on extracellular ACh and choline levels, as measured by microdialysis, as well as the effects of nimodipine under hypoxia. Microdialysis guide cannulae were implanted into the hippocampal region of male Fischer rats so that probes would sample from the CA1 and DG regions. Animals were then exposed for eight hours to a simulated altitude of 5,500 m (18,000 ft) or tested at sea level for an equivalent duration. HPLC with electrochemical detection was used for analysis of the dialysates. At 5,500 m extracellular ACh levels in the placebo-treated group were significantly lower than the sea level group values. This decrement was reversed by nimodipine administered i.p. immediately preceding altitude ascent (10 mg/kg) and 250 min post-altitude ascent (10 mg/kg). These data suggest that nimodipine may provide protection from the detrimental effects of hypoxia on hippocampal cholinergic function.

A latex mask for collection of expired gases from goats.

A latex respiratory mask was developed to collect expired gas from goats in studies of ventilatory adaptation to high altitude. The snouts of 15 animals were dimensioned by taking girth measurements. The procedure requires a rough positive mold of wood which is repeatedly submerged into latex, then slowly rotated upon removal until skim-like layers form a mask. A supporting harness is attached to the mask by use of three flat straps connected by Dot fasteners. A period of several hours per day for up to 2 weeks may be necessary to allow the animal to become accustomed to wearing the mask.

The use of tympanometry to detect aerotitis media in hypobaric chamber operations.

Diagnosis and quantification of aerotitis media were performed using a modified commercially-available tympanometer under hypobaric conditions. Subjects were 22 males and 9 females, 22-43 years of age, who were tested in each ear with the tympanometer prior to and after exposure, sequentially at the barometric pressure plateaus of 706, 656, 609, 586, 564, and 522 mm Hg, and following an induced ear block during a 1-min descent from 522 to 586 mm Hg. Each subject was examined once either alone or in pairs during a 90-min exposure. Aerotitis media was detected using tympanometry at simulated altitude as evidenced by the difference between measurements made during induced ear blocks and those made prior to inducement, as well as following relief of the pressure differential with the Valsalva maneuver. There were no significant differences between pre- and post-induced aerotitis media values at 586 mm Hg, or between pre- and post-hypobaria. Our study suggests that tympanometry can be a valuable tool in managing aerotitis media in the aeromedical environment.

Symptomatology during hypoxic exposure to flame-retardant chamber atmospheres.

Hypoxia was studied in 12 men during 63-h exposures to 17 and 13% O2, with the subjects serving as their own controls by repeating the measurements in 21% O2. All test atmospheres were contaminated with 0.9% CO2 to simulate the condition of living aboard submarines. The mean SaO2's were 97-98% in all conditions of 21% O2, 96% in 17% O2 (n.s.), and 92% in 13% O2 (P less than 0.05). The blood concentrations of 2,3-diphosphoglycerate were elevated in 13 and 17% O2 (P less than 0.05). Seventeen percent O2 did not cause significant symptoms of environmental stress; however, 13% O2 caused symptoms of acute mountain sickness in 5 of 12 men. In the last 7 h of exposure to 17% O2, reduction of the barometric pressure to 576 Torr reduced the ambient PO2 to 98 Torr (similar to the PO2 of 13% O2 at normobaric pressure). This induced symptoms of acute mountain sickness in 3 of 11 men. All symptomatology and physiologic changes were reversed during recovery in 21% O2. Monitoring devices indicated the presence of volatile organic contaminants at a mean concentration of 6.1 ppm in the chamber atmosphere. Combustion tests in the occupied chamber showed that flame propagation was retarded by lowering the O2 concentration from 21 to 13-17%. We conclude that men can live comfortably in a normobaric, flame-retardant atmosphere consisting of 17% O2-0.9% CO2-6.1 ppm volatile organic compounds-balance N2.

A reusable adapter for collection of cerebrospinal fluid in chronically cannulated goats.

A lightweight, adjustable adapter has been designed for chronic cannulation of goats (Capra hircus) which provides an accurate, safe means of sampling cerebrospinal fluid (CSF). This cisternal cannula has been used for continuous perfusion of synthetic CSF into the fourth ventricle in unanesthetized goats. This method also has been used for examining changes in ionic composition of the CSF and cerebral interstitial fluid (ISF) during physiologic adaptations to high altitude (2-5).

An environmentally-controlled extended-use small animal hypobaric chamber.

An environmentally-controlled extended-use small animal hypobaric chamber has been designed to study small laboratory animals at low barometric pressures for long periods of exposure. The rectangular chamber (91.4 X 71.1 X 50.8 cm) is constructed of aluminum plate and acrylic resin with a volume of 3.3 X 10(5) cm3. A computer/data acquisition control unit provides for controlling and collecting data on pressure, temperature, and relative humidity (RH) for sustained operations. Altitude simulation is achieved using a two-stage, air-cooled vacuum pump with a displacement of 30 cm3 X min-1. The pressure within the chamber is controlled by an incremental throttling valve in the vacuum line. Temperature (0-100 degrees C) is accomplished by using a remote-controlled constant temperature circulating bath. RH (20-80%) is regulated by pre-conditioning the ventilation purge air prior to entering the chamber. Acceptable levels of oxygen and carbon dioxide gases are maintained by purging with sufficient volumes of fresh air.